I have two versions of python, /usr/bin/python  (version 2.7.10 in MacOS ) & /usr/local/bin/python(version 2.7.13 installed via brew).
I use pip (installed by brew install python )to install a module protobuf!
but /usr/bin/python cannot find the module protobuf,whereas the /usr/local/bin/python could find it. 
how can I make the /usr/bin/python to find the module
update
@RNB
according to the installation, sudo python get-pip.py  I have errors like 
:Collecting pip
  Downloading pip-9.0.1-py2.py3-none-any.whl (1.3MB)
    100% |████████████████████████████████| 1.3MB 640kB/s 
Collecting wheel
  Downloading wheel-0.29.0-py2.py3-none-any.whl (66kB)
    100% |████████████████████████████████| 71kB 6.3MB/s 
Installing collected packages: pip, wheel
  Found existing installation: pip 8.1.2
    Uninstalling pip-8.1.2:
      Successfully uninstalled pip-8.1.2
  Rolling back uninstall of pip
Exception:
Traceback (most recent call last):
  File "/tmp/tmpW2v8kJ/pip.zip/pip/basecommand.py", line 215, in main
  .....
    File"/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 235, in _compile
    cachekey = (type(key[0]),) + key
RuntimeError: maximum recursion depth exceeded while calling a Python object
solution
according to @RNB's advice, first clean all pip packages,uninstall brew python+pip,  install pip for sys's python by python get-pip.py, maybe it gives error with wheel, so set options --no-setuptools&--no-wheel for python get-pip.py,install or upgrade setuptools & wheel via pip.At last install protobuf,problem solved!
 
     
    