cpython-lru_cache-weakref: Doc/libtypes.tex annotate

annotate Doc/libtypes.tex @ 4566:6403c94de50d legacy-trunk

Added safeguard against failure in __del__.

author	Guido van Rossum <guido@python.org>
date	Wed, 27 Nov 1996 19:39:58 +0000
parents	1e2d280606d1
children	efdee7d43270

rev	line source
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	1 \section{Built-in Types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	2
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	3 The following sections describe the standard types that are built into
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	4 the interpreter. These are the numeric types, sequence types, and
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	5 several others, including types themselves. There is no explicit
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	6 Boolean type; use integers instead.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	7 \indexii{built-in}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	8 \indexii{Boolean}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	9
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	10 Some operations are supported by several object types; in particular,
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	11 all objects can be compared, tested for truth value, and converted to
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	12 a string (with the \code{`{\rm \ldots}`} notation). The latter conversion is
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	13 implicitly used when an object is written by the \code{print} statement.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	14 \stindex{print}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	15
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	16 \subsection{Truth Value Testing}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	17
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	18 Any object can be tested for truth value, for use in an \code{if} or
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	19 \code{while} condition or as operand of the Boolean operations below.
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	20 The following values are considered false:
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	21 \stindex{if}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	22 \stindex{while}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	23 \indexii{truth}{value}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	24 \indexii{Boolean}{operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	25 \index{false}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	26
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	27 \begin{itemize}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	28 \renewcommand{\indexsubitem}{(Built-in object)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	29
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	30 \item \code{None}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	31 \ttindex{None}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	32
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	33 \item zero of any numeric type, e.g., \code{0}, \code{0L}, \code{0.0}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	34
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	35 \item any empty sequence, e.g., \code{''}, \code{()}, \code{[]}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	36
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	37 \item any empty mapping, e.g., \code{\{\}}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	38
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	39 \item instances of user-defined classes, if the class defines a
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	40 \code{__nonzero__()} or \code{__len__()} method, when that
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	41 method returns zero.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	42
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	43 \end{itemize}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	44
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	45 All other values are considered true --- so objects of many types are
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	46 always true.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	47 \index{true}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	48
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	49 Operations and built-in functions that have a Boolean result always
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	50 return \code{0} for false and \code{1} for true, unless otherwise
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	51 stated. (Important exception: the Boolean operations \samp{or} and
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	52 \samp{and} always return one of their operands.)
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	53
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	54 \subsection{Boolean Operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	55
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	56 These are the Boolean operations, ordered by ascending priority:
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	57 \indexii{Boolean}{operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	58
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	59 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	60 \lineiii{\var{x} or \var{y}}{if \var{x} is false, then \var{y}, else \var{x}}{(1)}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	61 \hline
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	62 \lineiii{\var{x} and \var{y}}{if \var{x} is false, then \var{x}, else \var{y}}{(1)}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	63 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	64 \lineiii{not \var{x}}{if \var{x} is false, then \code{1}, else \code{0}}{(2)}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	65 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	66 \opindex{and}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	67 \opindex{or}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	68 \opindex{not}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	69
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	70 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	71 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	72
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	73 \begin{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	74
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	75 \item[(1)]
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	76 These only evaluate their second argument if needed for their outcome.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	77
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	78 \item[(2)]
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	79 \samp{not} has a lower priority than non-Boolean operators, so e.g.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	80 \code{not a == b} is interpreted as \code{not(a == b)}, and
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	81 \code{a == not b} is a syntax error.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	82
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	83 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	84
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	85 \subsection{Comparisons}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	86
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	87 Comparison operations are supported by all objects. They all have the
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	88 same priority (which is higher than that of the Boolean operations).
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	89 Comparisons can be chained arbitrarily, e.g. \code{x < y <= z} is
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	90 equivalent to \code{x < y and y <= z}, except that \code{y} is
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	91 evaluated only once (but in both cases \code{z} is not evaluated at
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	92 all when \code{x < y} is found to be false).
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	93 \indexii{chaining}{comparisons}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	94
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	95 This table summarizes the comparison operations:
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	96
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	97 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Meaning}{Notes}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	98 \lineiii{<}{strictly less than}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	99 \lineiii{<=}{less than or equal}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	100 \lineiii{>}{strictly greater than}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	101 \lineiii{>=}{greater than or equal}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	102 \lineiii{==}{equal}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	103 \lineiii{<>}{not equal}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	104 \lineiii{!=}{not equal}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	105 \lineiii{is}{object identity}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	106 \lineiii{is not}{negated object identity}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	107 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	108 \indexii{operator}{comparison}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	109 \opindex{==} % XXX All others have funny characters < ! >
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	110 \opindex{is}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	111 \opindex{is not}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	112
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	113 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	114 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	115
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	116 \begin{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	117
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	118 \item[(1)]
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	119 \code{<>} and \code{!=} are alternate spellings for the same operator.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	120 (I couldn't choose between \ABC{} and \C{}! :-)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	121 \indexii{\ABC{}}{language}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	122 \indexii{\C{}}{language}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	123
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	124 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	125
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	126 Objects of different types, except different numeric types, never
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	127 compare equal; such objects are ordered consistently but arbitrarily
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	128 (so that sorting a heterogeneous array yields a consistent result).
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	129 Furthermore, some types (e.g., windows) support only a degenerate
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	130 notion of comparison where any two objects of that type are unequal.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	131 Again, such objects are ordered arbitrarily but consistently.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	132 \indexii{types}{numeric}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	133 \indexii{objects}{comparing}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	134
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	135 (Implementation note: objects of different types except numbers are
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	136 ordered by their type names; objects of the same types that don't
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	137 support proper comparison are ordered by their address.)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	138
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	139 Two more operations with the same syntactic priority, \code{in} and
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	140 \code{not in}, are supported only by sequence types (below).
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	141 \opindex{in}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	142 \opindex{not in}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	143
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	144 \subsection{Numeric Types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	145
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	146 There are three numeric types: \dfn{plain integers}, \dfn{long integers}, and
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	147 \dfn{floating point numbers}. Plain integers (also just called \dfn{integers})
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	148 are implemented using \code{long} in \C{}, which gives them at least 32
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	149 bits of precision. Long integers have unlimited precision. Floating
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	150 point numbers are implemented using \code{double} in \C{}. All bets on
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	151 their precision are off unless you happen to know the machine you are
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	152 working with.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	153 \indexii{numeric}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	154 \indexii{integer}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	155 \indexii{integer}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	156 \indexiii{long}{integer}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	157 \indexii{floating point}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	158 \indexii{\C{}}{language}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	159
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	160 Numbers are created by numeric literals or as the result of built-in
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	161 functions and operators. Unadorned integer literals (including hex
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	162 and octal numbers) yield plain integers. Integer literals with an \samp{L}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	163 or \samp{l} suffix yield long integers
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	164 (\samp{L} is preferred because \code{1l} looks too much like eleven!).
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	165 Numeric literals containing a decimal point or an exponent sign yield
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	166 floating point numbers.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	167 \indexii{numeric}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	168 \indexii{integer}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	169 \indexiii{long}{integer}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	170 \indexii{floating point}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	171 \indexii{hexadecimal}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	172 \indexii{octal}{literals}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	173
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	174 Python fully supports mixed arithmetic: when a binary arithmetic
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	175 operator has operands of different numeric types, the operand with the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	176 ``smaller'' type is converted to that of the other, where plain
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	177 integer is smaller than long integer is smaller than floating point.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	178 Comparisons between numbers of mixed type use the same rule.%
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	179 \footnote{As a consequence, the list \code{[1, 2]} is considered equal
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	180 to \code{[1.0, 2.0]}, and similar for tuples.}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	181 The functions \code{int()}, \code{long()} and \code{float()} can be used
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	182 to coerce numbers to a specific type.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	183 \index{arithmetic}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	184 \bifuncindex{int}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	185 \bifuncindex{long}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	186 \bifuncindex{float}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	187
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	188 All numeric types support the following operations, sorted by
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	189 ascending priority (operations in the same box have the same
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	190 priority; all numeric operations have a higher priority than
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	191 comparison operations):
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	192
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	193 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	194 \lineiii{\var{x} + \var{y}}{sum of \var{x} and \var{y}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	195 \lineiii{\var{x} - \var{y}}{difference of \var{x} and \var{y}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	196 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	197 \lineiii{\var{x} * \var{y}}{product of \var{x} and \var{y}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	198 \lineiii{\var{x} / \var{y}}{quotient of \var{x} and \var{y}}{(1)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	199 \lineiii{\var{x} \%{} \var{y}}{remainder of \code{\var{x} / \var{y}}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	200 \hline
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	201 \lineiii{-\var{x}}{\var{x} negated}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	202 \lineiii{+\var{x}}{\var{x} unchanged}{}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	203 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	204 \lineiii{abs(\var{x})}{absolute value of \var{x}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	205 \lineiii{int(\var{x})}{\var{x} converted to integer}{(2)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	206 \lineiii{long(\var{x})}{\var{x} converted to long integer}{(2)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	207 \lineiii{float(\var{x})}{\var{x} converted to floating point}{}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	208 \lineiii{divmod(\var{x}, \var{y})}{the pair \code{(\var{x} / \var{y}, \var{x} \%{} \var{y})}}{(3)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	209 \lineiii{pow(\var{x}, \var{y})}{\var{x} to the power \var{y}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	210 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	211 \indexiii{operations on}{numeric}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	212
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	213 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	214 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	215 \begin{description}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	216
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	217 \item[(1)]
2945 f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	218 For (plain or long) integer division, the result is an integer.
f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	219 The result is always rounded towards minus infinity: 1/2 is 0,
f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	220 (-1)/2 is -1, 1/(-2) is -1, and (-1)/(-2) is 0.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	221 \indexii{integer}{division}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	222 \indexiii{long}{integer}{division}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	223
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	224 \item[(2)]
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	225 Conversion from floating point to (long or plain) integer may round or
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	226 truncate as in \C{}; see functions \code{floor()} and \code{ceil()} in
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	227 module \code{math} for well-defined conversions.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	228 \bifuncindex{floor}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	229 \bifuncindex{ceil}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	230 \indexii{numeric}{conversions}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	231 \stmodindex{math}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	232 \indexii{\C{}}{language}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	233
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	234 \item[(3)]
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	235 See the section on built-in functions for an exact definition.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	236
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	237 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	238 % XXXJH exceptions: overflow (when? what operations?) zerodivision
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	239
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	240 \subsubsection{Bit-string Operations on Integer Types}
2581 4d28b655b728 added nodename macro calls for new very long section names Guido van Rossum <guido@python.org> parents: 2576 diff changeset	241 \nodename{Bit-string Operations}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	242
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	243 Plain and long integer types support additional operations that make
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	244 sense only for bit-strings. Negative numbers are treated as their 2's
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	245 complement value (for long integers, this assumes a sufficiently large
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	246 number of bits that no overflow occurs during the operation).
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	247
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	248 The priorities of the binary bit-wise operations are all lower than
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	249 the numeric operations and higher than the comparisons; the unary
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	250 operation \samp{~} has the same priority as the other unary numeric
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	251 operations (\samp{+} and \samp{-}).
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	252
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	253 This table lists the bit-string operations sorted in ascending
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	254 priority (operations in the same box have the same priority):
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	255
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	256 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	257 \lineiii{\var{x} \| \var{y}}{bitwise \dfn{or} of \var{x} and \var{y}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	258 \hline
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	259 \lineiii{\var{x} \^{} \var{y}}{bitwise \dfn{exclusive or} of \var{x} and \var{y}}{}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	260 \hline
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	261 \lineiii{\var{x} \&{} \var{y}}{bitwise \dfn{and} of \var{x} and \var{y}}{}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	262 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	263 \lineiii{\var{x} << \var{n}}{\var{x} shifted left by \var{n} bits}{(1), (2)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	264 \lineiii{\var{x} >> \var{n}}{\var{x} shifted right by \var{n} bits}{(1), (3)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	265 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	266 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	267 \lineiii{\~\var{x}}{the bits of \var{x} inverted}{}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	268 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	269 \indexiii{operations on}{integer}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	270 \indexii{bit-string}{operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	271 \indexii{shifting}{operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	272 \indexii{masking}{operations}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	273
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	274 \noindent
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	275 Notes:
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	276 \begin{description}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	277 \item[(1)] Negative shift counts are illegal.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	278 \item[(2)] A left shift by \var{n} bits is equivalent to
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	279 multiplication by \code{pow(2, \var{n})} without overflow check.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	280 \item[(3)] A right shift by \var{n} bits is equivalent to
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	281 division by \code{pow(2, \var{n})} without overflow check.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	282 \end{description}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	283
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	284 \subsection{Sequence Types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	285
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	286 There are three sequence types: strings, lists and tuples.
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	287
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	288 Strings literals are written in single or double quotes:
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	289 \code{'xyzzy'}, \code{"frobozz"}. See Chapter 2 of the Python
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	290 Reference Manual for more about string literals. Lists are
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	291 constructed with square brackets, separating items with commas:
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	292 \code{[a, b, c]}. Tuples are constructed by the comma operator (not
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	293 within square brackets), with or without enclosing parentheses, but an
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	294 empty tuple must have the enclosing parentheses, e.g.,
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	295 \code{a, b, c} or \code{()}. A single item tuple must have a trailing
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	296 comma, e.g., \code{(d,)}.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	297 \indexii{sequence}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	298 \indexii{string}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	299 \indexii{tuple}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	300 \indexii{list}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	301
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	302 Sequence types support the following operations. The \samp{in} and
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	303 \samp{not\,in} operations have the same priorities as the comparison
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	304 operations. The \samp{+} and \samp{*} operations have the same
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	305 priority as the corresponding numeric operations.\footnote{They must
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	306 have since the parser can't tell the type of the operands.}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	307
2647 9b7e6d9a528d typos, layout and other small things Guido van Rossum <guido@python.org> parents: 2609 diff changeset	308 This table lists the sequence operations sorted in ascending priority
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	309 (operations in the same box have the same priority). In the table,
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	310 \var{s} and \var{t} are sequences of the same type; \var{n}, \var{i}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	311 and \var{j} are integers:
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	312
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	313 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	314 \lineiii{\var{x} in \var{s}}{\code{1} if an item of \var{s} is equal to \var{x}, else \code{0}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	315 \lineiii{\var{x} not in \var{s}}{\code{0} if an item of \var{s} is
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	316 equal to \var{x}, else \code{1}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	317 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	318 \lineiii{\var{s} + \var{t}}{the concatenation of \var{s} and \var{t}}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	319 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	320 \lineiii{\var{s} * \var{n}{\rm ,} \var{n} * \var{s}}{\var{n} copies of \var{s} concatenated}{}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	321 \hline
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	322 \lineiii{\var{s}[\var{i}]}{\var{i}'th item of \var{s}, origin 0}{(1)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	323 \lineiii{\var{s}[\var{i}:\var{j}]}{slice of \var{s} from \var{i} to \var{j}}{(1), (2)}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	324 \hline
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	325 \lineiii{len(\var{s})}{length of \var{s}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	326 \lineiii{min(\var{s})}{smallest item of \var{s}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	327 \lineiii{max(\var{s})}{largest item of \var{s}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	328 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	329 \indexiii{operations on}{sequence}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	330 \bifuncindex{len}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	331 \bifuncindex{min}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	332 \bifuncindex{max}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	333 \indexii{concatenation}{operation}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	334 \indexii{repetition}{operation}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	335 \indexii{subscript}{operation}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	336 \indexii{slice}{operation}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	337 \opindex{in}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	338 \opindex{not in}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	339
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	340 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	341 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	342
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	343 \begin{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	344
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	345 \item[(1)] If \var{i} or \var{j} is negative, the index is relative to
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	346 the end of the string, i.e., \code{len(\var{s}) + \var{i}} or
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	347 \code{len(\var{s}) + \var{j}} is substituted. But note that \code{-0} is
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	348 still \code{0}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	349
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	350 \item[(2)] The slice of \var{s} from \var{i} to \var{j} is defined as
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	351 the sequence of items with index \var{k} such that \code{\var{i} <=
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	352 \var{k} < \var{j}}. If \var{i} or \var{j} is greater than
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	353 \code{len(\var{s})}, use \code{len(\var{s})}. If \var{i} is omitted,
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	354 use \code{0}. If \var{j} is omitted, use \code{len(\var{s})}. If
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	355 \var{i} is greater than or equal to \var{j}, the slice is empty.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	356
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	357 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	358
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	359 \subsubsection{More String Operations}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	360
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	361 String objects have one unique built-in operation: the \code{\%}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	362 operator (modulo) with a string left argument interprets this string
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	363 as a C sprintf format string to be applied to the right argument, and
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	364 returns the string resulting from this formatting operation.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	365
1683 080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	366 The right argument should be a tuple with one item for each argument
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	367 required by the format string; if the string requires a single
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	368 argument, the right argument may also be a single non-tuple object.%
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	369 \footnote{A tuple object in this case should be a singleton.}
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	370 The following format characters are understood:
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	371 \%, c, s, i, d, u, o, x, X, e, E, f, g, G.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	372 Width and precision may be a * to specify that an integer argument
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	373 specifies the actual width or precision. The flag characters -, +,
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	374 blank, \# and 0 are understood. The size specifiers h, l or L may be
1591 ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	375 present but are ignored. The \code{\%s} conversion takes any Python
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	376 object and converts it to a string using \code{str()} before
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	377 formatting it. The ANSI features \code{\%p} and \code{\%n}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	378 are not supported. Since Python strings have an explicit length,
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	379 \code{\%s} conversions don't assume that \code{'\e0'} is the end of
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	380 the string.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	381
1625 96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	382 For safety reasons, floating point precisions are clipped to 50;
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	383 \code{\%f} conversions for numbers whose absolute value is over 1e25
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	384 are replaced by \code{\%g} conversions.%
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	385 \footnote{These numbers are fairly arbitrary. They are intended to
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	386 avoid printing endless strings of meaningless digits without hampering
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	387 correct use and without having to know the exact precision of floating
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	388 point values on a particular machine.}
96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	389 All other errors raise exceptions.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	390
1591 ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	391 If the right argument is a dictionary (or any kind of mapping), then
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	392 the formats in the string must have a parenthesized key into that
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	393 dictionary inserted immediately after the \code{\%} character, and
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	394 each format formats the corresponding entry from the mapping. E.g.
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	395 \begin{verbatim}
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	396 >>> count = 2
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	397 >>> language = 'Python'
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	398 >>> print '%(language)s has %(count)03d quote types.' % vars()
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	399 Python has 002 quote types.
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	400 >>>
ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	401 \end{verbatim}
4404 1e2d280606d1 (libtypes.tex): Correct reversal of two words in description of Fred Drake <fdrake@acm.org> parents: 4401 diff changeset	402 In this case no * specifiers may occur in a format (since they
1e2d280606d1 (libtypes.tex): Correct reversal of two words in description of Fred Drake <fdrake@acm.org> parents: 4401 diff changeset	403 require a sequential parameter list).
1591 ac9e12b4ea8c Documented new built-in function vars(). Guido van Rossum <guido@python.org> parents: 1471 diff changeset	404
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	405 Additional string operations are defined in standard module
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	406 \code{string} and in built-in module \code{regex}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	407 \index{string}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	408 \index{regex}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	409
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	410 \subsubsection{Mutable Sequence Types}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	411
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	412 List objects support additional operations that allow in-place
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	413 modification of the object.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	414 These operations would be supported by other mutable sequence types
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	415 (when added to the language) as well.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	416 Strings and tuples are immutable sequence types and such objects cannot
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	417 be modified once created.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	418 The following operations are defined on mutable sequence types (where
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	419 \var{x} is an arbitrary object):
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	420 \indexiii{mutable}{sequence}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	421 \indexii{list}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	422
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	423 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	424 \lineiii{\var{s}[\var{i}] = \var{x}}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	425 {item \var{i} of \var{s} is replaced by \var{x}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	426 \lineiii{\var{s}[\var{i}:\var{j}] = \var{t}}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	427 {slice of \var{s} from \var{i} to \var{j} is replaced by \var{t}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	428 \lineiii{del \var{s}[\var{i}:\var{j}]}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	429 {same as \code{\var{s}[\var{i}:\var{j}] = []}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	430 \lineiii{\var{s}.append(\var{x})}
1625 96d0dc4739ec * Doc/libtypes.tex: fix typo in table of list methods; clarify Guido van Rossum <guido@python.org> parents: 1591 diff changeset	431 {same as \code{\var{s}[len(\var{s}):len(\var{s})] = [\var{x}]}}{}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	432 \lineiii{\var{s}.count(\var{x})}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	433 {return number of \var{i}'s for which \code{\var{s}[\var{i}] == \var{x}}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	434 \lineiii{\var{s}.index(\var{x})}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	435 {return smallest \var{i} such that \code{\var{s}[\var{i}] == \var{x}}}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	436 \lineiii{\var{s}.insert(\var{i}, \var{x})}
2819 8225c6581b3d correct description of list.insert() Guido van Rossum <guido@python.org> parents: 2647 diff changeset	437 {same as \code{\var{s}[\var{i}:\var{i}] = [\var{x}]}
8225c6581b3d correct description of list.insert() Guido van Rossum <guido@python.org> parents: 2647 diff changeset	438 if \code{\var{i} >= 0}}{}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	439 \lineiii{\var{s}.remove(\var{x})}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	440 {same as \code{del \var{s}[\var{s}.index(\var{x})]}}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	441 \lineiii{\var{s}.reverse()}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	442 {reverses the items of \var{s} in place}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	443 \lineiii{\var{s}.sort()}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	444 {permutes the items of \var{s} to satisfy
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	445 \code{\var{s}[\var{i}] <= \var{s}[\var{j}]},
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	446 for \code{\var{i} < \var{j}}}{(2)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	447 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	448 \indexiv{operations on}{mutable}{sequence}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	449 \indexiii{operations on}{sequence}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	450 \indexiii{operations on}{list}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	451 \indexii{subscript}{assignment}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	452 \indexii{slice}{assignment}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	453 \stindex{del}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	454 \renewcommand{\indexsubitem}{(list method)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	455 \ttindex{append}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	456 \ttindex{count}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	457 \ttindex{index}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	458 \ttindex{insert}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	459 \ttindex{remove}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	460 \ttindex{reverse}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	461 \ttindex{sort}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	462
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	463 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	464 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	465 \begin{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	466 \item[(1)] Raises an exception when \var{x} is not found in \var{s}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	467
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	468 \item[(2)] The \code{sort()} method takes an optional argument
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	469 specifying a comparison function of two arguments (list items) which
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	470 should return \code{-1}, \code{0} or \code{1} depending on whether the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	471 first argument is considered smaller than, equal to, or larger than the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	472 second argument. Note that this slows the sorting process down
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	473 considerably; e.g. to sort a list in reverse order it is much faster
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	474 to use calls to \code{sort()} and \code{reverse()} than to use
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	475 \code{sort()} with a comparison function that reverses the ordering of
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	476 the elements.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	477 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	478
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	479 \subsection{Mapping Types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	480
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	481 A \dfn{mapping} object maps values of one type (the key type) to
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	482 arbitrary objects. Mappings are mutable objects. There is currently
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	483 only one standard mapping type, the \dfn{dictionary}. A dictionary's keys are
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	484 almost arbitrary values. The only types of values not acceptable as
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	485 keys are values containing lists or dictionaries or other mutable
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	486 types that are compared by value rather than by object identity.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	487 Numeric types used for keys obey the normal rules for numeric
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	488 comparison: if two numbers compare equal (e.g. 1 and 1.0) then they
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	489 can be used interchangeably to index the same dictionary entry.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	490
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	491 \indexii{mapping}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	492 \indexii{dictionary}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	493
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	494 Dictionaries are created by placing a comma-separated list of
4401 d16b8621a3f0 Typos detected by Sjoerd Guido van Rossum <guido@python.org> parents: 3543 diff changeset	495 \code{\var{key}:\,\var{value}} pairs within braces, for example:
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	496 \code{\{'jack':\,4098, 'sjoerd':\,4127\}} or
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	497 \code{\{4098:\,'jack', 4127:\,'sjoerd'\}}.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	498
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	499 The following operations are defined on mappings (where \var{a} is a
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	500 mapping, \var{k} is a key and \var{x} is an arbitrary object):
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	501
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	502 \begin{tableiii}{\|c\|l\|c\|}{code}{Operation}{Result}{Notes}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	503 \lineiii{len(\var{a})}{the number of items in \var{a}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	504 \lineiii{\var{a}[\var{k}]}{the item of \var{a} with key \var{k}}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	505 \lineiii{\var{a}[\var{k}] = \var{x}}{set \code{\var{a}[\var{k}]} to \var{x}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	506 \lineiii{del \var{a}[\var{k}]}{remove \code{\var{a}[\var{k}]} from \var{a}}{(1)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	507 \lineiii{\var{a}.items()}{a copy of \var{a}'s list of (key, item) pairs}{(2)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	508 \lineiii{\var{a}.keys()}{a copy of \var{a}'s list of keys}{(2)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	509 \lineiii{\var{a}.values()}{a copy of \var{a}'s list of values}{(2)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	510 \lineiii{\var{a}.has_key(\var{k})}{\code{1} if \var{a} has a key \var{k}, else \code{0}}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	511 \end{tableiii}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	512 \indexiii{operations on}{mapping}{types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	513 \indexiii{operations on}{dictionary}{type}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	514 \stindex{del}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	515 \bifuncindex{len}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	516 \renewcommand{\indexsubitem}{(dictionary method)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	517 \ttindex{keys}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	518 \ttindex{has_key}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	519
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	520 \noindent
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	521 Notes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	522 \begin{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	523 \item[(1)] Raises an exception if \var{k} is not in the map.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	524
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	525 \item[(2)] Keys and values are listed in random order.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	526 \end{description}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	527
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	528 \subsection{Other Built-in Types}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	529
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	530 The interpreter supports several other kinds of objects.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	531 Most of these support only one or two operations.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	532
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	533 \subsubsection{Modules}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	534
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	535 The only special operation on a module is attribute access:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	536 \code{\var{m}.\var{name}}, where \var{m} is a module and \var{name} accesses
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	537 a name defined in \var{m}'s symbol table. Module attributes can be
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	538 assigned to. (Note that the \code{import} statement is not, strictly
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	539 spoken, an operation on a module object; \code{import \var{foo}} does not
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	540 require a module object named \var{foo} to exist, rather it requires
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	541 an (external) \emph{definition} for a module named \var{foo}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	542 somewhere.)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	543
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	544 A special member of every module is \code{__dict__}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	545 This is the dictionary containing the module's symbol table.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	546 Modifying this dictionary will actually change the module's symbol
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	547 table, but direct assignment to the \code{__dict__} attribute is not
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	548 possible (i.e., you can write \code{\var{m}.__dict__['a'] = 1}, which
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	549 defines \code{\var{m}.a} to be \code{1}, but you can't write \code{\var{m}.__dict__ = \{\}}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	550
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	551 Modules are written like this: \code{<module 'sys'>}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	552
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	553 \subsubsection{Classes and Class Instances}
2581 4d28b655b728 added nodename macro calls for new very long section names Guido van Rossum <guido@python.org> parents: 2576 diff changeset	554 \nodename{Classes and Instances}
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	555
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	556 (See Chapters 3 and 7 of the Python Reference Manual for these.)
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	557
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	558 \subsubsection{Functions}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	559
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	560 Function objects are created by function definitions. The only
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	561 operation on a function object is to call it:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	562 \code{\var{func}(\var{argument-list})}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	563
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	564 There are really two flavors of function objects: built-in functions
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	565 and user-defined functions. Both support the same operation (to call
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	566 the function), but the implementation is different, hence the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	567 different object types.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	568
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	569 The implementation adds two special read-only attributes:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	570 \code{\var{f}.func_code} is a function's \dfn{code object} (see below) and
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	571 \code{\var{f}.func_globals} is the dictionary used as the function's
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	572 global name space (this is the same as \code{\var{m}.__dict__} where
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	573 \var{m} is the module in which the function \var{f} was defined).
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	574
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	575 \subsubsection{Methods}
2488 80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	576 \obindex{method}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	577
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	578 Methods are functions that are called using the attribute notation.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	579 There are two flavors: built-in methods (such as \code{append()} on
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	580 lists) and class instance methods. Built-in methods are described
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	581 with the types that support them.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	582
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	583 The implementation adds two special read-only attributes to class
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	584 instance methods: \code{\var{m}.im_self} is the object whose method this
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	585 is, and \code{\var{m}.im_func} is the function implementing the method.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	586 Calling \code{\var{m}(\var{arg-1}, \var{arg-2}, {\rm \ldots},
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	587 \var{arg-n})} is completely equivalent to calling
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	588 \code{\var{m}.im_func(\var{m}.im_self, \var{arg-1}, \var{arg-2}, {\rm
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	589 \ldots}, \var{arg-n})}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	590
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	591 (See the Python Reference Manual for more info.)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	592
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	593 \subsubsection{Code Objects}
2488 80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	594 \obindex{code}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	595
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	596 Code objects are used by the implementation to represent
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	597 ``pseudo-compiled'' executable Python code such as a function body.
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	598 They differ from function objects because they don't contain a
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	599 reference to their global execution environment. Code objects are
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	600 returned by the built-in \code{compile()} function and can be
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	601 extracted from function objects through their \code{func_code}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	602 attribute.
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	603 \bifuncindex{compile}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	604 \ttindex{func_code}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	605
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	606 A code object can be executed or evaluated by passing it (instead of a
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	607 source string) to the \code{exec} statement or the built-in
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	608 \code{eval()} function.
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	609 \stindex{exec}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	610 \bifuncindex{eval}
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	611
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	612 (See the Python Reference Manual for more info.)
80729aff9057 added code objects Guido van Rossum <guido@python.org> parents: 2064 diff changeset	613
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	614 \subsubsection{Type Objects}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	615
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	616 Type objects represent the various object types. An object's type is
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	617 accessed by the built-in function \code{type()}. There are no special
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	618 operations on types. The standard module \code{types} defines names
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	619 for all standard built-in types.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	620 \bifuncindex{type}
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	621 \stmodindex{types}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	622
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	623 Types are written like this: \code{<type 'int'>}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	624
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	625 \subsubsection{The Null Object}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	626
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	627 This object is returned by functions that don't explicitly return a
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	628 value. It supports no special operations. There is exactly one null
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	629 object, named \code{None} (a built-in name).
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	630
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	631 It is written as \code{None}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	632
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	633 \subsubsection{File Objects}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	634
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	635 File objects are implemented using \C{}'s \code{stdio} package and can be
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	636 created with the built-in function \code{open()} described under
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	637 Built-in Functions below. They are also returned by some other
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	638 built-in functions and methods, e.g.\ \code{posix.popen()} and
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	639 \code{posix.fdopen()} and the \code{makefile()} method of socket
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	640 objects.
7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	641 \bifuncindex{open}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	642
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	643 When a file operation fails for an I/O-related reason, the exception
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	644 \code{IOError} is raised. This includes situations where the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	645 operation is not defined for some reason, like \code{seek()} on a tty
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	646 device or writing a file opened for reading.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	647
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	648 Files have the following methods:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	649
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	650
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	651 \renewcommand{\indexsubitem}{(file method)}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	652
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	653 \begin{funcdesc}{close}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	654 Close the file. A closed file cannot be read or written anymore.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	655 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	656
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	657 \begin{funcdesc}{flush}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	658 Flush the internal buffer, like \code{stdio}'s \code{fflush()}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	659 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	660
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	661 \begin{funcdesc}{isatty}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	662 Return \code{1} if the file is connected to a tty(-like) device, else
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	663 \code{0}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	664 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	665
2945 f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	666 \begin{funcdesc}{read}{\optional{size}}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	667 Read at most \var{size} bytes from the file (less if the read hits
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	668 \EOF{} or no more data is immediately available on a pipe, tty or
2945 f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	669 similar device). If the \var{size} argument is negative or omitted,
f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	670 read all data until \EOF{} is reached. The bytes are returned as a string
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	671 object. An empty string is returned when \EOF{} is encountered
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	672 immediately. (For certain files, like ttys, it makes sense to
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	673 continue reading after an \EOF{} is hit.)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	674 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	675
2993 5d4749a470b4 Fixed incorrect tex-code for readline Jack Jansen <jack.jansen@cwi.nl> parents: 2945 diff changeset	676 \begin{funcdesc}{readline}{\optional{size}}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	677 Read one entire line from the file. A trailing newline character is
2064 280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	678 kept in the string%
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	679 \footnote{The advantage of leaving the newline on is that an empty string
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	680 can be returned to mean \EOF{} without being ambiguous. Another
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	681 advantage is that (in cases where it might matter, e.g. if you
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	682 want to make an exact copy of a file while scanning its lines)
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	683 you can tell whether the last line of a file ended in a newline
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	684 or not (yes this happens!).}
280f31e6c653 copyright.tex: Add 1995 to copyright message. Guido van Rossum <guido@python.org> parents: 1683 diff changeset	685 (but may be absent when a file ends with an
4401 d16b8621a3f0 Typos detected by Sjoerd Guido van Rossum <guido@python.org> parents: 3543 diff changeset	686 incomplete line). If the \var{size} argument is present and
2945 f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	687 non-negative, it is a maximum byte count (including the trailing
f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	688 newline) and an incomplete line may be returned.
f17b7d0a7482 correct description of integer division; describe optional read arg Guido van Rossum <guido@python.org> parents: 2819 diff changeset	689 An empty string is returned when \EOF{} is hit
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	690 immediately. Note: unlike \code{stdio}'s \code{fgets()}, the returned
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	691 string contains null characters (\code{'\e 0'}) if they occurred in the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	692 input.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	693 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	694
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	695 \begin{funcdesc}{readlines}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	696 Read until \EOF{} using \code{readline()} and return a list containing
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	697 the lines thus read.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	698 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	699
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	700 \begin{funcdesc}{seek}{offset\, whence}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	701 Set the file's current position, like \code{stdio}'s \code{fseek()}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	702 The \var{whence} argument is optional and defaults to \code{0}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	703 (absolute file positioning); other values are \code{1} (seek
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	704 relative to the current position) and \code{2} (seek relative to the
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	705 file's end). There is no return value.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	706 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	707
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	708 \begin{funcdesc}{tell}{}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	709 Return the file's current position, like \code{stdio}'s \code{ftell()}.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	710 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	711
3543 22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	712 \begin{funcdesc}{truncate}{\optional{size}}
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	713 Truncate the file's size. If the optional size argument present, the
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	714 file is truncated to (at most) that size. The size defaults to the
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	715 current position. Availability of this function depends on the
4401 d16b8621a3f0 Typos detected by Sjoerd Guido van Rossum <guido@python.org> parents: 3543 diff changeset	716 operating system version (e.g., not all \UNIX{} versions support this
3543 22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	717 operation).
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	718 \end{funcdesc}
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	719
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	720 \begin{funcdesc}{write}{str}
3543 22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	721 Write a string to the file. There is no return value. Note: due to
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	722 buffering, the string may not actually show up in the file until
22d7f54c5792 Removed some spurios biindex calls. Guido van Rossum <guido@python.org> parents: 2993 diff changeset	723 the \code{flush()} or \code{close()} method is called.
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	724 \end{funcdesc}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	725
1683 080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	726 \begin{funcdesc}{writelines}{list}
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	727 Write a list of strings to the file. There is no return value.
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	728 (The name is intended to match \code{readlines}; \code{writelines}
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	729 does not add line separators.)
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	730 \end{funcdesc}
080811b1d023 documented writelines() Guido van Rossum <guido@python.org> parents: 1625 diff changeset	731
2576 f47bc5554418 mass changes; fix titles; add examples; correct typos; clarifications; Guido van Rossum <guido@python.org> parents: 2488 diff changeset	732 \subsubsection{Internal Objects}
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	733
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	734 (See the Python Reference Manual for these.)
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	735
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	736 \subsection{Special Attributes}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	737
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	738 The implementation adds a few special read-only attributes to several
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	739 object types, where they are relevant:
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	740
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	741 \begin{itemize}
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	742
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	743 \item
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	744 \code{\var{x}.__dict__} is a dictionary of some sort used to store an
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	745 object's (writable) attributes;
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	746
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	747 \item
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	748 \code{\var{x}.__methods__} lists the methods of many built-in object types,
2609 7ef72873e4d6 restructured library manual accordiung to functional group Guido van Rossum <guido@python.org> parents: 2581 diff changeset	749 e.g., \code{[].__methods__} yields
1471 2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	750 \code{['append', 'count', 'index', 'insert', 'remove', 'reverse', 'sort']};
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	751
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	752 \item
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	753 \code{\var{x}.__members__} lists data attributes;
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	754
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	755 \item
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	756 \code{\var{x}.__class__} is the class to which a class instance belongs;
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	757
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	758 \item
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	759 \code{\var{x}.__bases__} is the tuple of base classes of a class object.
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	760
2ec96140a36b Restructured library documentation Guido van Rossum <guido@python.org> parents: diff changeset	761 \end{itemize}

Mercurial > cpython-lru_cache-weakref

annotate Doc/libtypes.tex @ 4566:6403c94de50d legacy-trunk