Why can't environmental variables set in python persist?

Question

I was hoping to write a python script to create some appropriate environmental variables by running the script in whatever directory I\'ll be executing some simulation code,

Answer 1

One workaround is to output export commands, and have the parent shell evaluate this..

thescript.py:

import pipes
import random
r = random.randint(1,100)
print("export BLAHBLAH=%s" % (pipes.quote(str(r))))

..and the bash alias (the same can be done in most shells.. even tcsh!):

alias setblahblahenv="eval $(python thescript.py)"

Usage:

$ echo $BLAHBLAH

$ setblahblahenv
$ echo $BLAHBLAH
72

You can output any arbitrary shell code, including multiple commands like:

export BLAHBLAH=23 SECONDENVVAR='something else' && echo 'everything worked'

Just remember to be careful about escaping any dynamically created output (the pipes.quote module is good for this)