how set/change env var PYTHONOPTIMIZE in Python 3 / 3.7 / 3.8 ????

[Gribouillis]

With IDLE in python 3.8 it works for me if I open IDLE with the -O switch on the command line

Output:
python3.8 -O -m idlelib

It seems that idle propagates the -O flag to the scripts that it runs.

With Thonny, it didn't work with the -O flag, but it worked with this command line (in linux)

Output:
PYTHONOPTIMIZE=1 python3.8 -m thonny