How do I find out my PYTHONPATH using Python?

Question

How do I find out which directories are listed in my system’s PYTHONPATH variable, from within a Python script (or the interactive shell)?

Answer 1

You would probably also want this:

import sys
print(sys.path)

Or as a one liner from the terminal:

python -c "import sys; print('\n'.join(sys.path))"

---

Caveat: If you have multiple versions of Python installed you should use a corresponding command python2 or python3.

Answer 2

sys.path might include items that aren't specifically in your PYTHONPATH environment variable. To query the variable directly, use:

import os
try:
    user_paths = os.environ['PYTHONPATH'].split(os.pathsep)
except KeyError:
    user_paths = []

Answer 3

Can't seem to edit the other answer. Has a minor error in that it is Windows-only. The more generic solution is to use os.pathsep as below:

sys.path might include items that aren't specifically in your PYTHONPATH environment variable. To query the variable directly, use:

import os
os.environ.get('PYTHONPATH', '').split(os.pathsep)

Answer 4

PYTHONPATH is an environment variable whose value is a list of directories. Once set, it is used by Python to search for imported modules, along with other std. and 3rd-party library directories listed in Python's "sys.path".

As any other environment variables, you can either export it in shell or in ~/.bashrc, see here. You can query os.environ['PYTHONPATH'] for its value in Python as shown below:

$ python3 -c "import os, sys; print(os.environ['PYTHONPATH']); print(sys.path) if 'PYTHONPATH' in sorted(os.environ) else print('PYTHONPATH is not defined')"

IF defined in shell as

$ export PYTHONPATH=$HOME/Documents/DjangoTutorial/mysite

THEN result =>

/home/Documents/DjangoTutorial/mysite
['', '/home/Documents/DjangoTutorial/mysite', '/usr/local/lib/python37.zip', '/usr/local/lib/python3.7', '/usr/local/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/site-packages']

ELSE result =>

PYTHONPATH is not defined

To set PYTHONPATH to multiple paths, see here.

Note that one can add or delete a search path via sys.path.insert(), del or remove() at run-time, but NOT through os.environ[]. Example:

>>> os.environ['PYTHONPATH']="$HOME/Documents/DjangoTutorial/mysite"
>>> 'PYTHONPATH' in sorted(os.environ)
True
>>> sys.path // but Not there
['', '/usr/local/lib/python37.zip', '/usr/local/lib/python3.7', '/usr/local/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/site-packages']

>>> sys.path.insert(0,os.environ['PYTHONPATH'])
>>> sys.path // It's there
['$HOME/Documents/DjangoTutorial/mysite', '', '/usr/local/lib/python37.zip', '/usr/local/lib/python3.7', '/usr/local/lib/python3.7/lib-dynload', '/usr/local/lib/python3.7/site-packages']
>>> 

In summary, PYTHONPATH is one way of specifying the Python search path(s) for imported modules in sys.path. You can also apply list operations directly to sys.path without the aid of PYTHONPATH.

Answer 5

Works in windows 10, essentially identical to vanuan's answer, but cleaner (taken from somewhere, can't remember where..):

import sys
for p in sys.path:
    print(p)

Answer 6

import subprocess
python_path = subprocess.check_output("which python", shell=True).strip()
python_path = python_path.decode('utf-8')

Answer 7

Python tells me where it lives when it gives me an error message :)

>>> import os
>>> os.environ['PYTHONPATH'].split(os.pathsep)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\martin\AppData\Local\Programs\Python\Python36-32\lib\os.py", line 669, in __getitem__
    raise KeyError(key) from None
KeyError: 'PYTHONPATH'
>>>

Answer 8

If using conda, you can get the env prefix using os.environ["CONDA_PREFIX"].

Answer 9

import sys
for a in sys.path:
    a = a.replace('\\\\','\\')
    print(a)

It will give all the paths ready for place in the Windows.

Answer 10

Use the command,

$ which python

remember to enter this in the correct environment so use:

$ conda activate <env>

or

$ mamba activate <env>

If you do not have a conda environment, $ which python or $ which python3 would do just fine.