using_pythonpath.rst

Putting stuff on the Python path

Remember the Python path?

.. nbplot::

    >>> import sys
    >>> print('\n'.join(sys.path))
    ...

We are going to be using the modules in fmri-methods-2015/for_exercises this week.

It may get tiring to keep doing:

import sys
sys.path.append('/Users/mb312/code/fmri-methods-2015/for_exercises')

Is there any easier way?

Why yes - there is. In fact there are several.

The one we are going to use is the PYTHONPATH environment variable (see https://docs.python.org/2/using/cmdline.html#envvar-PYTHONPATH).

If you are on a Mac

• Open Terminal.app;

• Open the file ~/.bash_profile in your text editor;

• Add the following line to the end:

  export PYTHONPATH=$HOME/code/fmri-methods-2015/for_exercises
  

Save the file. * Close Terminal.app; * Start Terminal.app again, and type this:

echo $PYTHONPATH

It should show something like /Users/your_username/fmri-methods-2015/for_exercises. If not, come get one of us.

If you are on Linux

• Open your favorite terminal program;

• Open the file ~/.bashrc in your text editor;

• Add the following line to the end:

  export PYTHONPATH=$HOME/fmri-methods-2015/for_exercises
  

  Save the file.

• Close your terminal application;

• Start your terminal application again, and type this:

  echo $PYTHONPATH
  

It should show something like /home/your_username/fmri-methods-2015/for_exercises. If not, come get one of us.

If you are on Windows

Got to the Windows menu, right-click on "Computer" and select "Properties":

From the computer properties dialog, select "Advanced system settings" on the left:

From the advanced system settings dialog, choose the "Environment variables" button:

In the Environment variables dialog, click the "New" button in the top half of the dialog, to make a new user variable:

Give the variable name as PYTHONPATH and the value is the path to the fmri-methods-2015/for_exercises directory. Choose OK and OK again to save this variable.

Now open a cmd Window (Windows key, then type cmd and press Return). Type:

echo %PYTHONPATH%

to confirm the environment variable is correctly set:

If you want the IPython notebook to see this new PYTHONPATH variable, you may need to close your terminal, open it again, and restart ipython notebook, so that it picks up PYTHONPATH from the environment settings.

You can check the current setting of environment variables, using the os.environ dictionary:

.. nbplot::

    >>> import os
    >>> os.environ['PYTHONPATH']