Why are PATH args to subprocess.run() not portable between Linux and MacOS?

I’m having difficulty with portability between Linux and MacOS with the subprocess.run() method.

On Linux, a command like below works just fine as long as someCommand is in my PATH (set in ~/.bashrc).

subprocess.run(["someCommand", "foo", "bar"])

However, on MacOS, the same command does not run, even though someCommand is in my PATH. Instead, I get an error like:

FileNotFoundError: [Errno 2] No such file or directory: 'someCommand'

There are many other answers on StackExchange which say “just use shell=True and convert the args list to a string”, which seems like a fine solution for me, but I am curious why Python on MacOS doesn’t seem to inherit PATH from the environment, while it clearly does on Linux. Can anyone clarify this for me, and/or point me to some relevant docs?

Answer

The problem on my Mac was that all the executables in my PATH were declared in ~/.bash_profile instead of ~/.bashrc.

I never knew this before today, but .bash_profile is only sourced on login shells, so I guess Python spawns a brand new non-login shell and doesn’t inherit the current shell environment that it was run in.

Thank you again to everyone who tried to help, I would have given up if it wasn’t for everyone’s comments!