python - how to access nargs of optparse-add_action? -

python - how to access nargs of optparse-add_action? -

i working on 1 requirement project using command line utility:optparse.

suppose if using add_option utility below:

parser.add_option('-c','--categories', dest='categories', nargs=4 )

i wanted add together check -c alternative if user not input 4 arguments.

something this:

if options.categories none: loop_iterate on nargs: options.categories[loop_iterate] = raw_input('enter input')

how access nargs of add_option().?

ps:i not want have check using print.help() , exit(-1)

please help.

afaik optparse doesn't provide value in public api via result of parse_args, don't need it. can name constant before using it:

num_categories = 4 # ... parser.add_option('-c', '--categories', dest='categories', nargs=num_categories) # later if not options.categories: options.categories = [raw_input('enter input: ') _ in range(num_categories)]

in fact add_option method returns option object have nargs field, do:

categories_opt = parser.add_option(..., nargs=4) # ... if not options.categories: options.categories = [raw_input('enter input: ') _ in range(categories_opt.nargs)]

however don't see how improve using costant in first place.

python python-2.7 optparse