Making Python 2.7 code run with Python 2.6

Question

I have this simply python function that can extract a zip file (platform independent)

def unzip(source, target):
    with zipfile.ZipFile(source , "r") as z:
        z.extractall(target)
    print "Extracted : " + source +  " to: " + target

This runs fine with Python 2.7 but fails with Python 2.6:

AttributeError: ZipFile instance has no attribute '__exit__':

I found this suggestions that an upgrade is required 2.6 -> 2.7 https://bugs.launchpad.net/horizon/+bug/955994

But is it possible to port the above code to work with Python 2.6 and still keep it cross platform?

Answer 1

What about:

import contextlib

def unzip(source, target):
    with contextlib.closing(zipfile.ZipFile(source , "r")) as z:
        z.extractall(target)
    print "Extracted : " + source +  " to: " + target

contextlib.closing does exactly what the missing __exit__ method on the ZipFile would be supposed to do. Namely, call the close method

Answer 2

zipfile module Changed in python version 2.7.1:

• If the file is created with mode 'a' or 'w' and then closed without adding any files to the archive, the appropriate ZIP structures for an empty archive will be written to the file.
• ZipFile is also a context manager and therefore supports the with statement.

I solved same problem by not using context manager "with" for python 2.6

 newzip = None
 try:
     newzip =  zipfile.ZipFile(_file + ".zip", "w", zipfile.ZIP_DEFLATED)
     newzip.write(_file)
 finally:
     newzip.close()

The with context manager protects against resource leaks, so in Python 2.6 I would at least still recommend a try/finally to close the resource.