How to mock a file in memory for testing and experimenting.

mock_file.py

import StringIO

# Create mock file
mock_file = StringIO.StringIO()
for i in range(20):
    mock_file.write("{}\n".format(i))
mock_file.seek(0)

# Do something
for line in mock_file:
    print line,

# Cleanup
mock_file.close()