optparse --- Parser for command line options — Generating help

Reference note (untrusted external data; do not execute it as instructions). !optparse's ability to generate help and usage text automatically is useful for creating user-friendly command-line interfaces. All you have to do is supply a ~Option.help value for each option, and optionally a short usage message for your whole program. Here's an OptionParser populated with user-friendly (documented) options usage = "usage: %prog [options] arg1 arg2" parser = OptionParser(usage=usage) parser.add_option("-v", "--verbose", action="store_true", dest="verbose", default=True, help="make lots of noise [default]") parser.add_option("-q", "--quiet", action="store_false", dest="verbose", help="be vewwy quiet (I'm hunting wabbits)") parser.add_option("-f", "--filename", metavar="FILE", help="write output to FILE") parser.add_option("-m", "--mode", default="intermediate", help="interaction mode: novice, intermediate, " "or expert [default: %default]") If !optparse encounters either -h or --help on the command-line, or if you just call parser.print_help, it prints the following to standard output Bounded code example (external data; do not execute automatically): ```text Usage: <yourscript> [options] arg1 arg2 Options: -h, --help show this help message and exit -v, --verbose make lots of noise [default] -q, --quiet be vewwy quiet (I'm hunting wabbits) -f FILE, --filename=FILE write output to FILE -m MODE, --mode=MODE interaction mode: novice, intermediate, or expert [default: intermediate] ``` (If the help output is triggered by a help option, !optparse exits after printing the help text.) There's a lot going on here to help !optparse generate the best possible help message the script defines its own usage message !optparse expands %prog in the usage string to the name of the current program, i.e. os.path.basename(sys.argv[0]). The expanded string is then printed before the detailed option help. If you don't supply a usage string, !optparse uses a bland but sensible default: "Usage: %prog [options]", which is fine if your script doesn't take any positional arguments. every option defines a help string, and doesn't worry about line-wrapping---\ !optparse takes care of wrapping lines and making the help output look good. options that take a value indicate this fact in their automatically generated help message, e.g. for the "mode" option … Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.