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What is PYTHONPATH

The PYTHONPATH is a variable in Python that the interpreter uses to locate modules by searching through the paths specified in sys.path.

sys.path is a list that includes, in order

  • The directory of the script (if applicable).
  • Paths specified in the environmental variable PYTHONPATH.
  • Other paths depending on the Python installation on your system.

So, when you import a module, Python searches through these paths in order to find the module.

For example, on my system

>>> import sys
>>> sys.path
['', '/usr/lib/python36.zip', '/usr/lib/python3.6', '/usr/lib/python3.6/lib-dynload', 
'/usr/local/lib/python3.6/dist-packages', '/usr/lib/python3/dist-packages']

To view the value of PYTHONPATH

echo $PYTHONPATH

In Linux, you can add a new path to PYTHONPATH like this

export PYTHONPATH="$PYTHONPATH:/path/to/dir/"