ref: 03852d94083a33e0b10762c2225f2015f23c49d5
dir: /sys/src/cmd/python/Doc/lib/required_1.py/
import optparse class OptionParser (optparse.OptionParser): def check_required (self, opt): option = self.get_option(opt) # Assumes the option's 'default' is set to None! if getattr(self.values, option.dest) is None: self.error("%s option not supplied" % option) parser = OptionParser() parser.add_option("-v", action="count", dest="verbose") parser.add_option("-f", "--file", default=None) (options, args) = parser.parse_args() print "verbose:", options.verbose print "file:", options.file parser.check_required("-f")