:mod:`StringIO` --- Read and write strings as files
===================================================

.. module:: StringIO
   :synopsis: Read and write strings as if they were files.


This module implements a file-like class, :class:`StringIO`, that reads and
writes a string buffer (also known as *memory files*).  See the description of
file objects for operations (section :ref:`bltin-file-objects`). (For
standard strings, see :class:`str` and :class:`unicode`.)


.. class:: StringIO([buffer])

   When a :class:`StringIO` object is created, it can be initialized to an existing
   string by passing the string to the constructor. If no string is given, the
   :class:`StringIO` will start empty. In both cases, the initial file position
   starts at zero.

   The :class:`StringIO` object can accept either Unicode or 8-bit strings, but
   mixing the two may take some care.  If both are used, 8-bit strings that cannot
   be interpreted as 7-bit ASCII (that use the 8th bit) will cause a
   :exc:`UnicodeError` to be raised when :meth:`getvalue` is called.

The following methods of :class:`StringIO` objects require special mention:


.. method:: StringIO.getvalue()

   Retrieve the entire contents of the "file" at any time before the
   :class:`StringIO` object's :meth:`close` method is called.  See the note above
   for information about mixing Unicode and 8-bit strings; such mixing can cause
   this method to raise :exc:`UnicodeError`.


.. method:: StringIO.close()

   Free the memory buffer.  Attempting to do further operations with a closed
   :class:`StringIO` object will raise a :exc:`ValueError`.

Example usage::

   import StringIO

   output = StringIO.StringIO()
   output.write('First line.\n')
   print >>output, 'Second line.'

   # Retrieve file contents -- this will be
   # 'First line.\nSecond line.\n'
   contents = output.getvalue()

   # Close object and discard memory buffer --
   # .getvalue() will now raise an exception.
   output.close()