Update Python modules with pip (*nix/OS X)

update_pip_modules.py

#!/usr/bin/env python
 
import os 
import pip
 
dists = [] 
for dist in pip.get_installed_distributions():
    dists.append(dist.project_name)
 
for dist_name in sorted(dists, key=lambda s: s.lower()):
    cmd = "sudo pip install {0} -U".format(dist_name)
    print '#', cmd
    os.system(cmd)

If I run python .\PythonUpdateAll.py it returns:

Traceback (most recent call last):
  File ".\PythonUpdateAll.py", line 7, in <module>
    for dist in pip.get_installed_distributions():
AttributeError: module 'pip' has no attribute 'get_installed_distributions'