$ ipython
    -bash: ipython: command not found

$ pip show ipython
---
Metadata-Version: 2.0
Name: ipython
Version: 4.0.0
Summary: IPython: Productive Interactive Computing
Home-page: http://ipython.org
Author: The IPython Development Team
Author-email: ipython-dev@scipy.org
License: BSD
Location: /Library/Python/2.7/site-packages
Requires: traitlets, pickleshare, simplegeneric, decorator, gnureadline, appnope, pexpect