How to use export with Python on Linux

python linux export
Kevin Campion picture Kevin Campion · Oct 1, 2009 · Viewed 137.1k times · Source

I need to make an export like this in Python :

# export MY_DATA="my_export"

I've tried to do :

# -*- python-mode -*-
# -*- coding: utf-8 -*-
import os
os.system('export MY_DATA="my_export"')

But when I list export, "MY_DATA" not appear :

# export

How I can do an export with Python without saving "my_export" into a file ?

Answer

alex tingle picture alex tingle · Oct 1, 2009

export is a command that you give directly to the shell (e.g. bash), to tell it to add or modify one of its environment variables. You can't change your shell's environment from a child process (such as Python), it's just not possible.

Here's what's happening when you try os.system('export MY_DATA="my_export"')...

/bin/bash process, command `python yourscript.py` forks python subprocess
 |_
   /usr/bin/python process, command `os.system()` forks /bin/sh subprocess
    |_
      /bin/sh process, command `export ...` changes its local environment

When the bottom-most /bin/sh subprocess finishes running your export ... command, then it's discarded, along with the environment that you have just changed.

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