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: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()
:mod:`cStringIO` --- Faster version of :mod:`StringIO`
======================================================
.. module:: cStringIO
:synopsis: Faster version of StringIO, but not subclassable.
.. moduleauthor:: Jim Fulton <jim@zope.com>
.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
The module :mod:`cStringIO` provides an interface similar to that of the
:mod:`StringIO` module. Heavy use of :class:`StringIO.StringIO` objects can be
made more efficient by using the function :func:`StringIO` from this module
instead.
Since this module provides a factory function which returns objects of built-in
types, there's no way to build your own version using subclassing. It's not
possible to set attributes on it. Use the original :mod:`StringIO` module in
those cases.
Unlike the memory files implemented by the :mod:`StringIO` module, those
provided by this module are not able to accept Unicode strings that cannot be
encoded as plain ASCII strings.
Calling :func:`StringIO` with a Unicode string parameter populates
the object with the buffer representation of the Unicode string, instead of
encoding the string.
Another difference from the :mod:`StringIO` module is that calling
:func:`StringIO` with a string parameter creates a read-only object. Unlike an
object created without a string parameter, it does not have write methods.
These objects are not generally visible. They turn up in tracebacks as
:class:`StringI` and :class:`StringO`.
The following data objects are provided as well:
.. data:: InputType
The type object of the objects created by calling :func:`StringIO` with a string
parameter.
.. data:: OutputType
The type object of the objects returned by calling :func:`StringIO` with no
parameters.
There is a C API to the module as well; refer to the module source for more
information.
Example usage::
import cStringIO
output = cStringIO.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()
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