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Access environment variable in macOS from python

I had no .bash_profile file so I created one and the only line in it is this:
YOUTUBE_API=someRandomString
In my .zshrc file the first line is this:
source ~/.bash_profile
And from the command line I can run this:
echo $YOUTUBE_API
Which gives me a correct output (my API key).
But when I try to do it in Python it returns None:
import os
print(os.environ.get('YOUTUBE_API'))
I'm running python version 3.9.4. Any idea why, and how I may fix it?
Thank you

You need
export YOUTUBE_API=someRandomString
Otherwise, the variable is available to the local shell, but not to any subprocesses.

It only depends on where you run your code from:
if the process the code runs in has the variable set, it shouldn't be None
if you run the code inside another process, you'll get None
Explanation:
Each process ID gets it's own environment, stored in /proc/<pid>/environ file, where its local non-exported variables get stored. this path gets deleted as soon as the process stops.
The only way to make this work is to either export the variable in the shell, before launch the program, or run YOUTUBE_API=someRandomString python <your python file>

Check if python script was triggered by jenkins

i got a python script in my project. Depending on whether it was run manually or via Jenkins, I need to respond to it differently.
The only solution I came up with so far was to set an environment variable via Jenkins and check this var in the script.
Has anyone had a similar problem and could somehow solve it differently ?

If you only want to avoid setting an env variable, but still prefer using an existing env var you might want to use https://plugins.jenkins.io/envinject/#EnvInjectPlugin-BuildCauses which exposes following variables in the Env variables:
BUILD_CAUSE=MANUALTRIGGER
BUILD_CAUSE_MANUALTRIGGER=true in case of manual trigger. It internally checks which cause(s) triggered the build, which can be many like SCMTriggerCause, TimerTriggerCause etc.

Running 'export' command with Pythons 'subprocess' does not work

subprocess.run('export FOO=BAR', shell=True)
This simply doesn't work, and I have no idea why.
All I am trying to do I set an environment variable from my python (3.5.1) script, and when I run the above line, nothing happens. No errors are raised, and when I check the environment variable myself, it has not been set.
Other shell commands with subprocess.run() do work, such as ls and pwd, but not export.
.run() was added in Python 3.5 (in case you didn't recognise it), but I have also tried the above line with .call() and .Popen(), with no change in results.
I am aware that I can set environment variables in python with os.environ['FOO'] = "BAR", but I will be using shell commands a lot in my project, and I expect that I will need to string multiple commands together, which will make using export easier than os.environ.
My project will run on Linux, which is what my machine is running on.

It works fine; however, the variable setting only exists in the subprocess. You cannot affect the environment of the local process from a child.
os.environ is the correct solution, as it changes the environment of the local process, and those changes will be inherited by any process started with subprocess.run.
You can also use the env argument to run:
subprocess.run(["cmdname", "arg1", "arg number 2"], env=dict(FOO='BAR', **os.environ))
This runs the command in a modified environment that includes FOO=BAR without modifying the current environment.

Setting up a specific Python in Jenkins

I am quite new with configuring Jenkins or Python but I have to set up a unitary test in Jenkins. My program is in Python, but only works on Python 2.6 whereas the Jenkins version I should be using is 2.7, so I'm trying to set up Jenkins to set some environment variables so that it prepares launching the accurate Python for that specific test (it is part of a greater project that will successfully run several other tests that work well).
The idea I had was to set in the command to execute several environment variables like PATH, LD_LIBRARY_PATH and PYTHONPATH such as following in the "Execute shell" command line interpreter:
PYTHONPATH=/path/to/python2.6/lib:$PYTHONPATH
PATH=/path/to/python2.6/bin:$PATH
LD_LIBRARY_PATH=/path/to/python2.6/lib:$LD_LIBRARY_PATH
... however, it was still calling the wrong version of Python. Therefore, I forced these variables to:
PYTHONPATH=/path/to/python2.6/lib
PATH=/path/to/python2.6/bin
LD_LIBRARY_PATH=/path/to/python2.6/lib
... and I still get errors because the old version of Python is called instead, even if it should not appear in the PATH ... It appears Jenkins will remember the location of the old libraries however and will try loading them first.
How would I correctly set the environment in a "subproject" in Jenkins so that I can call a different version of Python?
Thank you and best regards,
~Stéphane

If you want your program to run with a specific version of the python interpreter, you indicate it in the shebang
#!/usr/bin/python2.6
#your code here

What i did in my Jenkins shell script using a specific python version was something like this when calling my unit test:
python3 src/test/unit_test.py
I was using it to use Python 3.X but it should work with 2.6 as well using:
python2.6 src/test/unit_test.py

Stupid me... I was indeed doing things correctly, I just had a part of my code that was overriding the PYTHONPATH value, so the solution I had found previously was good.
FYI, I modified my shebang, if it's of any help to anyone ;)

Is there a commandline flag to set PYTHONHOME?

I'm attempting to run python on a system that doesn't allow me to set environment variables. Is there a commandline flag to python that will set PYTHONHOME? I looked here: http://docs.python.org/release/2.3.5/inst/search-path.html but didn't see anything.
So, hopefully something like this:
python -magical_path_flag /my/python/install test.py
EDIT
Thanks for the responses everyone. I'm embarrassed to say I actually meant PYTHONHOME, not PYTHONPATH. (That's what I deserve for asking a question at 1:30 AM.) I've edited my quesiton.
Here's some more info. I'm trying to get python running on Android. I can run python -V no problem, but if I try and execute a script, I get:
I/ControlActivity(18340): Could not find platform independent libraries <prefix>
I/ControlActivity(18340): Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Unfortunately when using the ProcessBuilder and changing the environment variables on Android, it says that they're not modifiable and throws an exception. I'm able to pass all the command line flags I want, so I was hoping I could set PYTHONHOME that way.
I've tried creating a wrapping shell script which exports PYTHONHOME and then calls python but that didn't work. (Got the same error as before.)
Thanks,
Gabe

You could simply set it in your script -- sys.path is a regular, modifiable list. Something like:
import sys
sys.path.append("/path/to/libraries")
should do the trick

In UNIXy shells, you can set an environment variable just for the duration of one command by prepending the command with the environment variable setting:
$ PYTHONPATH=/my/python/install python test.py

If none of the other answers suit you, you can write a wrapper script that temporarily sets the environment variable then exec's your other script. For example:
python mywrapper.py -magical_path_flag /my/python/install test.py