2.5 The StringIO Module

The stringio module shown in Example 2-8 implements an in-memory file object. This object can be used as input or output to most functions that expect a standard file object.

Example 2-8. Using the StringIO Module to Read from a Static File

File: stringio-example-1.py

import StringIO

MESSAGE = "That man is depriving a village somewhere of a computer scientist."

file = StringIO.StringIO(MESSAGE)

print file.read()

That man is depriving a village somewhere of a computer scientist.

The StringIO class implements memory file versions of all methods available for built-in file objects, plus a getvalue method that returns the internal string value. Example 2-9 demonstrates this method.

Example 2-9. Using the StringIO Module to Write to a Memory File

File: stringio-example-2.py

import StringIO

file = StringIO.StringIO()
file.write("This man is no ordinary man. ")
file.write("This is Mr. F. G. Superman.")

print file.getvalue()

This man is no ordinary man. This is Mr. F. G. Superman.

StringIO can be used to capture redirected output from the Python interpreter, as shown in Example 2-10.

Example 2-10. Using the StringIO Module to Capture Output

File: stringio-example-3.py

import StringIO
import string, sys

stdout = sys.stdout

sys.stdout = file = StringIO.StringIO()

print """
According to Gbaya folktales, trickery and guile
are the best ways to defeat the python, king of
snakes, which was hatched from a dragon at the
world's start. -- National Geographic, May 1997
"""

sys.stdout = stdout

print string.upper(file.getvalue())

ACCORDING TO GBAYA FOLKTALES, TRICKERY AND GUILE
ARE THE BEST WAYS TO DEFEAT THE PYTHON, KING OF
SNAKES, WHICH WAS HATCHED FROM A DRAGON AT THE
WORLD'S START. -- NATIONAL GEOGRAPHIC, MAY 1997