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I have a Python 2.7 app that uses Tkinter. The problem is that I cannot read the environment variables I defined when I use Tkinter.

Was thinking this was a problem I am having with Python/Tkinter app, or how I am defining my environment variable or both. I have tried defining an environment variable in /etc/environment and /etc/profile folders on a Raspberry Pi 2 as the following

EXPORT USR_USR="ccj63078"

What is strange is I can read $PATH $HOME.

To debug I stripped my app down to this writing the contents to a text file. 

#!/usr/bin/python

import os, Tkinter

top = Tkinter.Tk()
vusr_usr = os.environ.get('USR_USR')
user_envd = open('user_envd.txt','w+')
user_envd.write('v_usr= ' + str(vusr_usr) + '\n')
user_envd.close()
top.mainloop()

I am not understanding why I can read PATH or HOME, but not one that I defined?

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  • What happens when you run your minimal example? Is vusr_usr equal to None? Also, did you reboot after adding the line USR_USR="whatever" to your /etc/environment (note: you don't need export there)? Also worth checking: what do you get if you run print os.environ (e.g. in IDLE)? Commented Aug 28, 2017 at 13:31
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    There is no command EXPORT. It should be export. Commented Aug 28, 2017 at 14:54
  • Thank you for responding. I changed the EXPORT to export and tried removing export in the /etc/environment and it is the same each way. Commented Aug 28, 2017 at 17:20
  • when I look at the text tile the value it returns is None. when I print os.environ the environment variables and their correct values are listed as I defined them. so it seems that they are there. Commented Aug 28, 2017 at 17:23

1 Answer 1

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There are several files involved during login process (e.g. ~/.profile, ~/.bashrc, /etc/profile, ...), not all of them are used in all cases. It depends on the way you log in (can be different if you log in locally or via ssh, from a cron job, ...)

Python's os.environ probably does not see the environment variable because it is not part of the current environment. Easy to check (no python involved, just shell) using env command or specifically for the case above env | grep USR_USR. Execute export USR_USR="ccj63078" and run the python script (or run the minimum python script to expose the variable: python -c "import os; print os.environ.get('USR_USR')"). It should be able to see the environment variable.

The last thing is to figure out why is the variable definition not read from the file it is defined in. It needs more detailed about the way how you log in. I'd suggest to start with putting it to ~/.bashrc (assuming you are running bash).

(edit)
When launching desktop during boot with autologin:

  1. /etc/profile and ~/.profile are sourced
  2. It is handled by /etc/X11/Xsession.d/75source-profile (comes with jessie releases)

If /etc/X11/Xsession.d/75source-profile is missing just recreate it with

[ -f /etc/profile ] && . /etc/profile
[ -f "$HOME/.profile" ] && . "$HOME/.profile"

and put your environment variable definition into ~/.profile

From a similar question discussed at http://raspberrypi.org/forums/viewtopic.php?f=28&t=37575

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  • Thank you. I added the export of the environment variables to ~/.bashrc and when I run the minimum script at the command line python test.py it now see's the environment variables and can use them in the python app! However, my app sits on the raspberry pi desktop with an icon that fires off a shell script that executes the python app. When I run it this way, it does not find the environment variables. Is there another location I should define the environment variables in?. Commented Aug 29, 2017 at 13:25
  • There are several ways. Probably the easiest is to add the environment variable to ~/.xinitrc (e.g. cp /etc/X11/xinit/xinitrc ~/.xinitrc and then add export USR_USR="ccj63078" just after the initial comment). Commented Aug 29, 2017 at 13:41
  • Thank you! That did it! It works now and the python app can read the environment variable I defined when the python app is executed from a shell script! I learned a lot about environment variables and I appreciate your help! Commented Aug 29, 2017 at 14:02
  • Unfortunately, what i thought was working, was working because I had added the export USR_USR="ccj63078" to my shell script that calls the python program and I had forgotten to take that out when testing the xinitrc. So copying the export USR_USR="ccj63078" into ~/.xinitrc did not make it available to my python app when executed from the .sh file. Is there another location I can try? Commented Aug 29, 2017 at 16:19
  • Sorry, I am not usually running desktop automatically. So this time I actually tried it. Commented Aug 29, 2017 at 16:35

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