The way how argparse currently parses option arguments is broken. If a long option requires an argument and it's value isn't specified together with the option (using --option=value syntax), then the following argument should be interpreted as that value, no matter what it looks like. There should be no guesses or heuristics here. That the behavior depends on whether some argument "looks like" a negative number is the most horrible. Argument parsing should follow simple, deterministic rules, preferably the same that used by standard getopt(3).