environment variables

main.py

import subprocess
import os

os.environ['MY_SECRET'] = 'oi :D'

ret = subprocess.run(["python3.6", "sub.py"], stdout=subprocess.PIPE)

if 'MY_SECRET' in ret.stdout.decode('utf-8'):
    print('pwned!')

safe.py

import subprocess
import os

os.environ['MY_SECRET'] = 'oi :D'

with subprocess.Popen(['python3.6', 'sub.py'],
                      stdout=subprocess.PIPE,
                      env={'PATH': os.environ['PATH']}) as proc:
    ret = proc.stdout.read()

if 'MY_SECRET' in ret.decode('utf-8'):
    print('pwned!')
else:
    print('safe!')

sub.py

import os

for k, v in os.environ.items():
    print(k, v)