paul j3 added the comment: I'm going to close this. At most it calls for a documentation change. But saying something like It must be compatible with argparse._SubParsersAction. will just confuse the average user. Any customization of this action class is an advanced topic, that requires familiarity with the code, not just the documentation. ---------- resolution: -> rejected stage: -> resolved status: open -> closed _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue23487> _______________________________________