In the Python version of Google App Engine, what is the easiest way to mock or subclass the File class so that software written to access files does not throw an exception?

Question

I would like to run some code on the Python version of Google App Engine that uses the built in File type. I’m looking for the easiest way to stop GAE from throwing errors due to illegal access. Has anyone already sub-classed or mocked File to read and write to memory rather than to the disk? I don’t need persistence, just the ability to simulate file access.

Answer 1

import __builtin__
import StringIO

class File(StringIO.StringIO):
  def __init__(self, *a, **k): pass

__builtin__.file = __builtin__.open = File

You'll surely want finer-grained simulation, but this works as a very rough first cut.