Develop Reference

How to access system environment variables using Python

I am aware that you can use os.environ['key'] to access an environment variable, but it appears that this function is localized to environment variables for the signed in user. I need to access the system environment variables. Is this possible?

You cannot do this using os.environ in python. You can, however, use os.system to run a commands such as:
sudo -Hiu $user env | grep $var
to access a variable from another user. This is a bit hacky, but it works. And your options are limited here.
Also -- why do you want to? You should have a process for setting the environment variables before this script is run at all, ideally.

How do I set an environment variable for airflow to use?

Airflow is returning an error when trying to run a DAG saying that it can't find an environment variable, which is odd because it's able to find 3 other environment variables that I'm storing as a Python variable. No issues with those variables at all.
I have all 4 variables in ~/.profile and have also done
export var1="varirable1"
export var2="varirable2"
export var3="varirable3"
export var4="varirable4"
Under what user does airflow run? I've done those export commands under sudo as well, so I thought they would be picked up by airflow when it runs the dag

Is it maybe because airflow uses non-login shell? Have you tried putting these lines in : ~/.bashrc instead of ~/.profile ?

As per this answer, the variables should be put in /etc/default/airflow (on Debian/Ubuntu) or /etc/sysconfig/airflow (on Centos/Redhat).

If you are just running a local instance you should be able to use environment variables like you expect. Remember that you need to set them in the shell that is running the webserver and scheduler though. If these are in your .profile, you may need to run source ~/.profile.

Access macOS environment variables from Python

I got a bunch of environment variables set with the launchctl command:
launchctl setenv TEST /Users/JohnDoe/Test
To get the value back, I can use:
launchctl getenv TEST
However, I can't access the value of TEST from Python, using os.getenv('TEST') (or even from Bash using echo $TEST). I do know how macOS manages environment variables (the difference between launchctl and Bash environment variables, etc.) so I understand why those commands don't return the value of TEST.
My question is: is there a way to access environment variables set with launchctl, without using subprocess? Using subprocess is not a no-go, I'd just rather avoid throwing lots of processes just to get environment variables :)

python: os.getenv returns none with sudo?

I've set environment variable LIBRARY_PATH in /etc/bash.bashrc by adding export LIBRARY_PATH=/usr/local/cuda/lib64:$LIBRARY_PATH at the end.
When I try to get the env-variable from python:
ipython
import os
print os.getenv('LIBRARY_PATH')
Everything works well, it prints /usr/local/cuda/lib64:.
BUT when I invoke ipython with sudo:
sudo ipython
import os
pront os.getenv('LIBRARY_PATH')
I get nothing. I guess this is about env-variables accross users, but what is the ditails? I set LIBRARY_PATH in /etc/bash.bashrc which is said to be the 'system wide bashrc file'.
So how can I get the correct env-variable with sudo in python ?

If you want sudo to pass through environment variables (which is generally considered a security hazard), use sudo -E.
Note that it is bash which executes the commands in the bashrc files. ipython is not bash, obviously, and sudo does not start up a shell process, much less a bash process, just in order to run the command you are requesting it to run. So none of your bashrc files are going to be executed by the sudo command or in the sudo subprocess. Of course, you can tell sudo to run a bash process:
sudo bash -c ipython
However, bash does not execute startup files if it detects that it is being run in a sudo process.
For more information on how sudo cleans the environment, type man 5 sudoers and skip down to the Command environment section.

If you set the environment variable in /root/.bash_profile, then you will probably get the desired behavior when using sudo.

How to set global environment variables using shell script .sh

I have a .sh file that locally sets some environment variables in my shell source my_env.sh.
#!/bin/sh
echo "Setting up local environment variables"
export MY_URL="http://domain.com"
echo "Done"
This only sets the variables for that session. Which means that my Python Celery and Supervisor apps which run under a different session cannot access them. I understand I can run them under a user, but I want to know if on Ubuntu using the same shell script above if I can set the variables so they are globally accessible to all applications regardless of users or session?

export your variables in the "/etc/profile".
NOTE: This will make it global for each shell sessions for any user. If you wish to set this variable for every session for a specific user, set it in that user's "~/.profile".

According to Ubuntu env variables doc the best way would be
A suitable file for environment variable settings that affect the system as a whole (rather than just a particular user) is /etc/environment
That's assuming you don't mind having them set for the whole machine.

If you are using bashrc or zshrc you can source the shell file which sets the environment variables across the sessions or precisely loads all the environment variables in each session.
source location/shell-script-sets-env.sh
The zshrc and bashrc is available in your $HOME directory. or ~/.zshrc and ~/.bashrc. The current shell can be looked via
echo $SHELL
Have a look at setting env permanently for adding it to the profile.