TRY to unset your python path…
In Linux/Mac, you can use these commands:
unset PYTHONPATH
unset PYTHONHOME
PYTHONHOME
Change the location of the standard Python libraries. By default, the
libraries are searched in prefix/lib/pythonversion and
exec_prefix/lib/pythonversion, where prefix and exec_prefix are
installation-dependent directories, both defaulting to /usr/local.
When PYTHONHOME is set to a single directory, its value replaces both
prefix and exec_prefix. To specify different values for these, set
PYTHONHOME to prefix:exec_prefix.
Try to clean up your PYTHONHOME:
user$ export PYTHONHOME=
As for installing matplotlib, I would recommend the following:
sudo apt-get install python-matplotlib
(details here)