StringIO -- Read and write strings as files

               
4.5 StringIO --
         Read and write strings as files
This module implements a file-like class, StringIO,
that reads and writes a string buffer (also known as memory
files).  See the description of file objects for operations (section
3.9
).
  class StringIO(
  [buffer])
When a 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 StringIO will start empty.
In both cases, the initial file position starts at zero.
The 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 UnicodeError to be raised
when getvalue() is called.
The following methods of StringIO objects require special
mention:
  getvalue(
  )
Retrieve the entire contents of the ``file'' at any time before the
StringIO object's 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 UnicodeError.
  close(
  )
Free the memory buffer.
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()
cStringIO --
         Faster version of StringIO
The module cStringIO provides an interface similar to that of
the
StringIO
module.  Heavy use of StringIO.StringIO
objects can be made more efficient by using the function
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.  Use the original
StringIO
module in that case.
Unlike the memory files implemented by the
StringIO
module, those provided by this module are not able to accept Unicode
strings that cannot be encoded as plain ASCII strings.
Calling 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
StringIO
module is that calling
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 StringI and StringO.
The following data objects are provided as well:
InputType
  The type object of the objects created by calling
  StringIO with a string parameter.
OutputType
  The type object of the objects returned by calling
  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()