Read environment variables in Python

Question

I have set some environment variables in ~/.profile:

SOMEVAR=/some/custom/path

and already did source ~/.profile. So when I do:

echo $SOMEVAR

it prints the correct directory:

/some/custom/path

However, when I try to read this variable in a Python script, it fails:

import os

print(os.environ["SOMEVAR"])

I get:

Traceback (most recent call last):
  File "environment_test.py", line 3, in <module>
    print os.environ["SOMEVAR"]
  File "/usr/lib64/python2.7/UserDict.py", line 23, in __getitem__
    raise KeyError(key)
KeyError: 'SOMEVAR'

What's wrong there?

Karoly Horvath · Accepted Answer · 2016-02-13 12:42:34Z

4

You don't want the launched processes see all the crap (= variables) you've created. Hence regular variables are only visible in this shell you're executing.

You have to export the variable:

export SOMEVAR=/some/custom/path

edited Feb 13, 2016 at 12:42

answered Feb 13, 2016 at 12:39

Karoly Horvath

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3 Comments

daniel451 Over a year ago

In ~/.profile? But why is echo $SOMEVAR working then?

Jonathon Reinhart Over a year ago

The variable is present in your shell (the process which sourced .profile) but it is not exported to child processes (your python script).

daniel451 Over a year ago

Wonderful, thank you for the explanation! I added the export and it works now :)

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