Mercurial > cpython-lru_cache-weakref
annotate Doc/lib/libstringio.tex @ 39940:dfd809dcf680 2.5
Bug #1446043: correctly raise a LookupError if an encoding name given
to encodings.search_function() contains a dot.
(backport from rev. 52075)
| author | Georg Brandl <georg@python.org> |
|---|---|
| date | Sat, 30 Sep 2006 11:22:35 +0000 |
| parents | 61c0fe48376a |
| children | 9918989b733b |
| rev | line source |
|---|---|
| 8918 | 1 \section{\module{StringIO} --- |
| 10661 | 2 Read and write strings as files} |
| 3 | |
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4 \declaremodule{standard}{StringIO} |
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5 \modulesynopsis{Read and write strings as if they were files.} |
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6 |
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7 |
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8 This module implements a file-like class, \class{StringIO}, |
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9 that reads and writes a string buffer (also known as \emph{memory |
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10 files}). See the description of file objects for operations (section |
| 10661 | 11 \ref{bltin-file-objects}). |
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12 |
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13 \begin{classdesc}{StringIO}{\optional{buffer}} |
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14 When a \class{StringIO} object is created, it can be initialized |
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15 to an existing string by passing the string to the constructor. |
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16 If no string is given, the \class{StringIO} will start empty. |
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17 In both cases, the initial file position starts at zero. |
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18 |
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19 The \class{StringIO} object can accept either Unicode or 8-bit |
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20 strings, but mixing the two may take some care. If both are used, |
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21 8-bit strings that cannot be interpreted as 7-bit \ASCII{} (that |
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22 use the 8th bit) will cause a \exception{UnicodeError} to be raised |
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23 when \method{getvalue()} is called. |
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24 \end{classdesc} |
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25 |
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26 The following methods of \class{StringIO} objects require special |
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27 mention: |
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28 |
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29 \begin{methoddesc}{getvalue}{} |
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30 Retrieve the entire contents of the ``file'' at any time before the |
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31 \class{StringIO} object's \method{close()} method is called. See the |
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32 note above for information about mixing Unicode and 8-bit strings; |
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33 such mixing can cause this method to raise \exception{UnicodeError}. |
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34 \end{methoddesc} |
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35 |
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36 \begin{methoddesc}{close}{} |
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37 Free the memory buffer. |
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38 \end{methoddesc} |
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39 |
| 39211 | 40 Example usage: |
| 41 | |
| 42 \begin{verbatim} | |
| 43 import StringIO | |
| 44 | |
| 45 output = StringIO.StringIO() | |
| 46 output.write('First line.\n') | |
| 47 print >>output, 'Second line.' | |
| 48 | |
| 49 # Retrieve file contents -- this will be | |
| 50 # 'First line.\nSecond line.\n' | |
| 51 contents = output.getvalue() | |
| 52 | |
| 53 # Close object and discard memory buffer -- | |
| 54 # .getvalue() will now raise an exception. | |
| 55 output.close() | |
| 56 \end{verbatim} | |
| 57 | |
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58 |
| 8918 | 59 \section{\module{cStringIO} --- |
| 10661 | 60 Faster version of \module{StringIO}} |
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61 |
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62 \declaremodule{builtin}{cStringIO} |
| 10661 | 63 \modulesynopsis{Faster version of \module{StringIO}, but not |
| 64 subclassable.} | |
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65 \moduleauthor{Jim Fulton}{jim@zope.com} |
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66 \sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org} |
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67 |
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68 The module \module{cStringIO} provides an interface similar to that of |
| 10661 | 69 the \refmodule{StringIO} module. Heavy use of \class{StringIO.StringIO} |
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70 objects can be made more efficient by using the function |
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71 \function{StringIO()} from this module instead. |
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72 |
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73 Since this module provides a factory function which returns objects of |
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74 built-in types, there's no way to build your own version using |
| 10661 | 75 subclassing. Use the original \refmodule{StringIO} module in that case. |
| 76 | |
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77 Unlike the memory files implemented by the \refmodule{StringIO} |
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78 module, those provided by this module are not able to accept Unicode |
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79 strings that cannot be encoded as plain \ASCII{} strings. |
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80 |
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81 Another difference from the \refmodule{StringIO} module is that calling |
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82 \function{StringIO()} with a string parameter creates a read-only object. |
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83 Unlike an object created without a string parameter, it does not have |
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84 write methods. These objects are not generally visible. They turn up in |
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85 tracebacks as \class{StringI} and \class{StringO}. |
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86 |
| 10661 | 87 The following data objects are provided as well: |
| 88 | |
| 89 | |
| 90 \begin{datadesc}{InputType} | |
| 91 The type object of the objects created by calling | |
| 92 \function{StringIO} with a string parameter. | |
| 93 \end{datadesc} | |
| 94 | |
| 95 \begin{datadesc}{OutputType} | |
| 96 The type object of the objects returned by calling | |
| 97 \function{StringIO} with no parameters. | |
| 98 \end{datadesc} | |
| 99 | |
| 100 | |
| 101 There is a C API to the module as well; refer to the module source for | |
| 102 more information. | |
| 39211 | 103 |
| 104 Example usage: | |
| 105 | |
| 106 \begin{verbatim} | |
| 107 import cStringIO | |
| 108 | |
| 109 output = cStringIO.StringIO() | |
| 110 output.write('First line.\n') | |
| 111 print >>output, 'Second line.' | |
| 112 | |
| 113 # Retrieve file contents -- this will be | |
| 114 # 'First line.\nSecond line.\n' | |
| 115 contents = output.getvalue() | |
| 116 | |
| 117 # Close object and discard memory buffer -- | |
| 118 # .getvalue() will now raise an exception. | |
| 119 output.close() | |
| 120 \end{verbatim} | |
| 121 |