title: ImportError: No module named 'xx' in mac and linux
body: <p>I am right now using the mac and trying to use the module pypng. I have installed the module from pip install pypng. It works well. However when I run my application python test.py (where inside test.py has 'import png'), it gives me a error saying 'ImportError:No module named png'.</p>
  
  <p>However when I go into the python environment from command line, I type 'import png', it works without a error, why is that. I even restart the computer, but still in trouble.</p>
  
  <p>when I installed pypng module, it tells me it is install in /Users/abc1/anaconda/lib/python2.7/site-packages, where inside this directory I can find the png.py and png.pyc.</p>
  
  <hr>
  
  <p>when i print sys.path, this is the output, looks like it didn't load the png package from /Users/abc1/anaconda/lib/python2.7/site-packages. how do i solve it</p>
  
  <pre><code>['/Applications/Blender/blender.app/Contents/Resources/2.76/scripts/addons_contrib', '/Applications/Blender/blender.app/Contents/Resources/2.76/scripts/addons', '/Applications/Blender/blender.app/Contents/Resources/2.76/scripts/modules', '/Applications/Blender/blender.app/Contents/Resources/2.76/scripts/startup', '/Applications/Blender/blender.app/Contents/MacOS/../Resources/2.76/scripts/modules', '/Applications/Blender/blender.app/Contents/Resources/2.76/python/lib/python34.zip', '/Applications/Blender/blender.app/Contents/Resources/2.76/python/lib/python3.4', '/Applications/Blender/blender.app/Contents/Resources/2.76/python/lib/python3.4/plat-darwin', '/Applications/Blender/blender.app/Contents/Resources/2.76/python/lib/python3.4/lib-dynload', '/Applications/Blender/blender.app/Contents/Resources/2.76/python/lib/python3.4/site-packages', '/Applications/Blender/blender.app/Contents/MacOS/../Resources/2.76/scripts/freestyle/modules', '/Applications/Blender/blender.app/Contents/Resources/2.76/scripts/addons/modules', '/Users/xisizhe/Library/Application Support/Blender/2.76/scripts/addons/modules']
  </code></pre>