python optparse treat next option as the option argument for the current one when it's missing

Question

I use optparse to parse the command options for my script. I have -f and -c options that both require an option argument. But when it's missing, it will treat the next option as option argument for the current option. e.g.

./myScript -f -c

this will treat "-c" as option argument for "-f" instead of complaining about option argument missing for "-f" and "-c". For other normal scenarios, it works fine.

Thank your for any information and solutions!

update： solution,by using argparse, this problem can be avoided. it exits with an error complaining about missing argument for options.

Answer 1

optparse is deprecated from python 2.7 on, so you should use the argparse module, which has this behaviour built in:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('-f')
parser.add_argument('-c')

parser.parse_args(['-f', 'f_val', '-c', 'c_val'])   #works as expected
parser.parse_args(['-f', '-c'])                     #errors as expected

If you are left with python < 2.7 and the optparse module, you can easily do it with a custom check after the parsing stage:

parser = OptionParser('usage')
parser.add_option("-f", "--ff", dest="f_value")
parser.add_option("-c", "--cc", dest="c_value")

(options, args) = parser.parse_args()

if options.f_value == '-c':
    print 'error: -f requires an argument'
    exit(1)