Why can't Python see environment variables? [duplicate]

Question

I'm working on Debian Jessie with Python 2. Why can't Python's environ see environment variables that are visible in bash?

# echo $SECRET_KEY
xxx-xxx-xxxx
# python
>>> from os import environ
>>> environ["SECRET_KEY"]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/root/.virtualenvs/prescribing/lib/python2.7/UserDict.py", line 23, in __getitem__
    raise KeyError(key)
KeyError: 'SECRET_KEY'

I set these environment variables using /etc/environment - not sure if that's relevant:

SECRET_KEY=xxx-xxx-xxx

I had to run source /etc/environment to get bash to see them, which I thought was strange.

UPDATE: printenv SECRET_KEY produces nothing, so I guess SECRET_KEY is a shell not an environment variable.

Answer 1

You need to export environment variables for child processes to see them:

export SECRET_KEY

Demo:

$ SECRET_KEY='foobar'
$ bin/python -c "import os; print os.environ.get('SECRET_KEY', 'Nonesuch')"
Nonesuch
$ export SECRET_KEY
$ bin/python -c "import os; print os.environ.get('SECRET_KEY', 'Nonesuch')"
foobar

You can combine the setting and exporting in one step:

export SECRET_KEY=xxx-xxx-xxxx

Note that new variables in /etc/environment do not show up in your existing shells automatically, not until you have a new login. For a GUI desktop, you'll have to log out and log in again, for SSH sessions you'll have to create a new SSH login. Only then will you get a new tree of processes with the changes present. Using source /etc/environment only sets 'local' variables (the file is not a script). See How to reload /etc/environment without rebooting? over on Super User.