Import globally installed module

Question

I am trying to execute my python script which imports globally installed modules through pip. (Module like nltk)

Below is my code.

interpreter.execfile("/home/roy/eclipse-workspace/geospatial-analysis/src/main/resources/wordnet_util.py");
    PyObject someFunc = interpreter.get("get_similarity");
    PyObject result = someFunc.__call__(new PyString("Apple pie."), new PyString("Banana pie."));
    Double realResult = (Double) result.__tojava__(Double.class);

I have added the path for python modules like,

import sys
sys.path.append("/usr/local/lib/python2.7/dist-packages")

But I get the following error,

*sys-package-mgr*: can't create package cache dir, '/usr/local/lib/python2.7/dist-packages/cachedir/packages'
Exception in thread "main" Traceback (most recent call last):
File "/home/roy/eclipse-workspace/geospatial-analysis/src/main/resources/wordnet_util.py", line 6, in <module>
from nltk import word_tokenize, pos_tag
File "/usr/local/lib/python2.7/dist-packages/nltk/__init__.py", line 18, in <module>
from __future__ import print_function, absolute_import
ImportError: No module named __future__

Update:

I added sys.path.append("/usr/lib/python2.7") to the python file. It solved the above error. Now it can't find select module.

ImportError: No module named signal