No module named six - even though six is installed

问题:

I'm trying to use matplotlib but I'm getting this error saying "No Module named six". I read previous answers and installed six using pip and also tried pip install six --upgrade. But nothing worked. What could be wrong?

EDIT:

The TraceBack:

Traceback (most recent call last):
  File "<string>", line 254, in run_nodebug
  File "C:\Users\Akshay\Documents\Internship.py", line 290, in <module>
    from matplotlib import pyplot
  File "C:\Python27\lib\site-packages\matplotlib\__init__.py", line 105, in <module>
    import six
ImportError: No module named six

And sorry I'm unfamiliar with the which command. I'm using Python 2.7, and the latest pip.