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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.

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    That's not an environment variable; it is just a shell variable until you export it. Commented Aug 13, 2015 at 16:40
  • Really? I thought /env/environment was for setting environment variables - is this incorrect? Commented Aug 13, 2015 at 16:44
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    Using source /env/environment only sets variables in the shell, not environment variables accessible by child processes. Commented Aug 13, 2015 at 16:46
  • Yes, no, maybe — yes, it is incorrect (because they're only environment variables if you export them); no, it is correct that /etc/environment might be used to set environment variables (though it isn't a standard file, AFAIK, but it is referenced in Ubuntu, it seems); maybe, because it depends what you write in the file (or what is written in the file if you don't have control over its contents). Commented Aug 13, 2015 at 16:46
  • What OS is this on? I've never seen /env/environment used, not for shells at any rate. Commented Aug 13, 2015 at 16:47

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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.

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8 Comments

I was trying to follow the instructions in help.ubuntu.com/community/… - should I use export foo-bar instead of foo=bar in /etc/environment?
It's worth noting that os.environ is only loaded the first time the os module is imported. So if you call a subprocess to execute a bash script, when it returns to the python script it won't be able to see the new environment variables that were possibly exported in your bash script.
@Richard: in your question you named it /env/environment, not /etc/environment.. I'm not that familiar with Ubuntu, I'll have a look as to how the OS is using those. Did you restart at all after making changes to the file?
@amza: a subprocess won't be able to set variables for the parent process anyway. This has nothing to do with os.environ being loaded when first imported (the mapping is actually built when Python starts). The process environment can only be altered by the current process or a parent process, and subprocess never creates such a process, so the distinction is entirely moot.
@Richard: a quick experiment shows that changes in /etc/environment only apply to new logins; after editing I didn't see the change in new subshells, but use ssh localhost and those new login sessions do see the new variable. So I suspect that this is used by PAM to set up the new user environment.
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