Roy Smith <roy@panix.com> added the comment: I just got bit by this in Python 3.5.3. I get why it does this. I also get why it's impractical to change the behavior now. But, it really isn't the obvious behavior, so it should be documented at https://docs.python.org/3.5/library/argparse.html?highlight=argparse#default. ---------- nosy: +roysmith _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue16399> _______________________________________