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Added tests for missing host to open_http and open_gopher
author Guido van Rossum <guido@python.org>
date Mon, 18 Apr 1994 09:39:56 +0000
parents 2ec96140a36b
children 907605320a5f
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 \section{Built-in Module \sectcode{sys}}
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2
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3 \bimodindex{sys}
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4 This module provides access to some variables used or maintained by the
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5 interpreter and to functions that interact strongly with the interpreter.
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6 It is always available.
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7
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8 \renewcommand{\indexsubitem}{(in module sys)}
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9 \begin{datadesc}{argv}
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10 The list of command line arguments passed to a Python script.
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11 \code{sys.argv[0]} is the script name.
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12 If no script name was passed to the Python interpreter,
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13 \code{sys.argv} is empty.
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14 \end{datadesc}
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15
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16 \begin{datadesc}{builtin_module_names}
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17 A list of strings giving the names of all modules that are compiled
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18 into this Python interpreter. (This information is not available in
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19 any other way --- \code{sys.modules.keys()} only lists the imported
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20 modules.)
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21 \end{datadesc}
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22
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23 \begin{datadesc}{exc_type}
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24 \dataline{exc_value}
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25 \dataline{exc_traceback}
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26 These three variables are not always defined; they are set when an
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27 exception handler (an \code{except} clause of a \code{try} statement) is
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28 invoked. Their meaning is: \code{exc_type} gets the exception type of
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29 the exception being handled; \code{exc_value} gets the exception
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30 parameter (its \dfn{associated value} or the second argument to
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31 \code{raise}); \code{exc_traceback} gets a traceback object which
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32 encapsulates the call stack at the point where the exception
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33 originally occurred.
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34 \end{datadesc}
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35
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36 \begin{funcdesc}{exit}{n}
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37 Exit from Python with numeric exit status \var{n}. This is
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38 implemented by raising the \code{SystemExit} exception, so cleanup
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39 actions specified by \code{finally} clauses of \code{try} statements
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40 are honored, and it is possible to catch the exit attempt at an outer
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41 level.
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42 \end{funcdesc}
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43
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44 \begin{datadesc}{exitfunc}
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45 This value is not actually defined by the module, but can be set by
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46 the user (or by a program) to specify a clean-up action at program
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47 exit. When set, it should be a parameterless function. This function
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48 will be called when the interpreter exits in any way (but not when a
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49 fatal error occurs: in that case the interpreter's internal state
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50 cannot be trusted).
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51 \end{datadesc}
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52
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53 \begin{datadesc}{last_type}
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54 \dataline{last_value}
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55 \dataline{last_traceback}
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56 These three variables are not always defined; they are set when an
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57 exception is not handled and the interpreter prints an error message
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58 and a stack traceback. Their intended use is to allow an interactive
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59 user to import a debugger module and engage in post-mortem debugging
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60 without having to re-execute the command that cause the error (which
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61 may be hard to reproduce). The meaning of the variables is the same
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62 as that of \code{exc_type}, \code{exc_value} and \code{exc_tracaback},
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63 respectively.
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64 \end{datadesc}
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65
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66 \begin{datadesc}{modules}
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67 Gives the list of modules that have already been loaded.
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68 This can be manipulated to force reloading of modules and other tricks.
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69 \end{datadesc}
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70
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71 \begin{datadesc}{path}
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72 A list of strings that specifies the search path for modules.
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73 Initialized from the environment variable \code{PYTHONPATH}, or an
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74 installation-dependent default.
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75 \end{datadesc}
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76
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77 \begin{datadesc}{ps1}
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78 \dataline{ps2}
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79 Strings specifying the primary and secondary prompt of the
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80 interpreter. These are only defined if the interpreter is in
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81 interactive mode. Their initial values in this case are
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82 \code{'>>> '} and \code{'... '}.
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83 \end{datadesc}
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84
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85 \begin{funcdesc}{settrace}{tracefunc}
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86 Set the system's trace function, which allows you to implement a
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87 Python source code debugger in Python. The standard modules
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88 \code{pdb} and \code{wdb} are such debuggers; the difference is that
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89 \code{wdb} uses windows and needs STDWIN, while \code{pdb} has a
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90 line-oriented interface not unlike dbx. See the file \file{pdb.doc}
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91 in the Python library source directory for more documentation (both
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92 about \code{pdb} and \code{sys.trace}).
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93 \end{funcdesc}
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94 \ttindex{pdb}
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95 \ttindex{wdb}
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96 \index{trace function}
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97
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98 \begin{funcdesc}{setprofile}{profilefunc}
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99 Set the system's profile function, which allows you to implement a
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100 Python source code profiler in Python. The system's profile function
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101 is called similarly to the system's trace function (see
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102 \code{sys.settrace}), but it isn't called for each executed line of
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103 code (only on call and return and when an exception occurs). Also,
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104 its return value is not used, so it can just return \code{None}.
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105 \end{funcdesc}
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106 \index{profile function}
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107
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108 \begin{datadesc}{stdin}
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109 \dataline{stdout}
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110 \dataline{stderr}
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111 File objects corresponding to the interpreter's standard input,
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112 output and error streams. \code{sys.stdin} is used for all
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113 interpreter input except for scripts but including calls to
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114 \code{input()} and \code{raw_input()}. \code{sys.stdout} is used
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115 for the output of \code{print} and expression statements and for the
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116 prompts of \code{input()} and \code{raw_input()}. The interpreter's
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117 own prompts and (almost all of) its error messages go to
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118 \code{sys.stderr}. \code{sys.stdout} and \code{sys.stderr} needn't
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119 be built-in file objects: any object is acceptable as long as it has
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120 a \code{write} method that takes a string argument.
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121 \end{datadesc}
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122
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123 \begin{datadesc}{tracebacklimit}
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124 When this variable is set to an integer value, it determines the
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125 maximum number of levels of traceback information printed when an
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126 unhandled exception occurs. The default is 1000. When set to 0 or
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127 less, all traceback information is suppressed and only the exception
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128 type and value are printed.
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129 \end{datadesc}