Doc/lib/libstringio.tex

   1 \section{\module{StringIO} ---
   2          Read and write strings as files}
   3
   4 \declaremodule{standard}{StringIO}
   5 \modulesynopsis{Read and write strings as if they were files.}
   6
   7
   8 This module implements a file-like class, \class{StringIO},
   9 that reads and writes a string buffer (also known as \emph{memory
  10 files}).  See the description of file objects for operations (section
  11 \ref{bltin-file-objects}).
  12
  13 \begin{classdesc}{StringIO}{\optional{buffer}}
  14 When a \class{StringIO} object is created, it can be initialized
  15 to an existing string by passing the string to the constructor.
  16 If no string is given, the \class{StringIO} will start empty.
  17
  18 The \class{StringIO} object can accept either Unicode or 8-bit
  19 strings, but mixing the two may take some care.  If both are used,
  20 8-bit strings that cannot be interpreted as 7-bit \ASCII{} (that
  21 use the 8th bit) will cause a \exception{UnicodeError} to be raised
  22 when \method{getvalue()} is called.
  23 \end{classdesc}
  24
  25 The following methods of \class{StringIO} objects require special
  26 mention:
  27
  28 \begin{methoddesc}{getvalue}{}
  29 Retrieve the entire contents of the ``file'' at any time before the
  30 \class{StringIO} object's \method{close()} method is called.  See the
  31 note above for information about mixing Unicode and 8-bit strings;
  32 such mixing can cause this method to raise \exception{UnicodeError}.
  33 \end{methoddesc}
  34
  35 \begin{methoddesc}{close}{}
  36 Free the memory buffer.
  37 \end{methoddesc}
  38
  39
  40 \section{\module{cStringIO} ---
  41          Faster version of \module{StringIO}}
  42
  43 \declaremodule{builtin}{cStringIO}
  44 \modulesynopsis{Faster version of \module{StringIO}, but not
  45                 subclassable.}
  46 \moduleauthor{Jim Fulton}{jfulton@digicool.com}
  47 \sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
  48
  49 The module \module{cStringIO} provides an interface similar to that of
  50 the \refmodule{StringIO} module.  Heavy use of \class{StringIO.StringIO}
  51 objects can be made more efficient by using the function
  52 \function{StringIO()} from this module instead.
  53
  54 Since this module provides a factory function which returns objects of
  55 built-in types, there's no way to build your own version using
  56 subclassing.  Use the original \refmodule{StringIO} module in that case.
  57
  58 Unlike the memory files implemented by the \refmodule{StringIO}
  59 module, those provided by this module are not able to accept Unicode
  60 strings that cannot be encoded as plain \ASCII{} strings.
  61
  62 Another difference from the \refmodule{StringIO} module is that calling
  63 \function{StringIO()} with a string parameter creates a read-only object.
  64 Unlike an object created without a string parameter, it does not have
  65 write methods.
  66
  67 The following data objects are provided as well:
  68
  69
  70 \begin{datadesc}{InputType}
  71   The type object of the objects created by calling
  72   \function{StringIO} with a string parameter.
  73 \end{datadesc}
  74
  75 \begin{datadesc}{OutputType}
  76   The type object of the objects returned by calling
  77   \function{StringIO} with no parameters.
  78 \end{datadesc}
  79
  80
  81 There is a C API to the module as well; refer to the module source for
  82 more information.