call method without args from argparse

Question

I have a method I call from the command line using argparse. I also want to call that method from another method, in this case I get an error saying args is not defined. Is there a way around this, I have tried setting a default but I get the same error.

def change_modem_bank(bank_num=None, modem=None):  
    if args.sim_bank and args.modem_num:
        bank_num = args.sim_bank
        modem = args.modem_num  
    if "1" in bank_num:
        print "2" 
    elif "2" in bank_num:
         print "2"
    print modem

if __name__=='__main__':            
    parser_mode = subparsers.add_parser('set_modem_bank')
    parser_mode.add_argument('-bank',dest='sim_bank',help='SIM bank number',nargs='?',const=None,default=None)
    parser_mode.add_argument('-modem_num',dest='modem_num',help='Modem number',nargs='?',const=None,default=None)
    parser_mode.set_defaults(func=change_modem_bank)
    args=parser.parse_args()
    args.func()

I want to call the method like so from another script:

import cellular_modem
cellular_modem.change_modem_bank("2","0")

Currently I can call it like this:

myscript.py set_modem_bank -bank ${num}  -modem ${modem_num}

I would like it to work with either type of call, from CLI and from inside a python script.

possible duplicate of [Calling functions with argparse](http://stackoverflow.com/questions/5050920/calling-functions-with-argparse) — skrrgwasme, May 15 '15 at 15:57
You need to give us more context. Where do you normally call `args=parser.parse_args`. — hpaulj, May 15 '15 at 16:21
@hpaulj it is called from main. So when in call it from CLI it works fine, I'll edit that into my code — Paul, May 15 '15 at 16:24
Make it clear how your method gets access to `args` in that `main` case. — hpaulj, May 15 '15 at 16:26

score 1 · Answer 1 · answered May 15 '15 at 16:39

Your change_modem_bank function tries to access args directly, which works when you call it as a command-line script since it's in the module namespace then, but fails when you call it separately. Just fix it to get args passed in instead:

def change_modem_bank(bank_num, modem):  
    if "1" in bank_num:
        print "2" 
    elif "2" in bank_num:
         print "2"
    print modem

And call it with:

args.func(args.sim_bank, args.modem_num)

You'll have to figure out what your function is supposed to do if the arguments are None, since that will cause an error now.

hpaulj · Accepted Answer · 2015-05-15T16:58:45.383

When you call it as a script, what happens is:

args=parser.parse_args()
change_modem_bank() # equivalent to args.func()

When you import the module, that main part is skipped, so args is not set. If you want to call change_modem_back as is, then you need to create an args variable that looks like the one that the parser would generate. Here's one way of doing that:

import cellular_modem
import argparse
args = argparse.Namepspace(simbank=xxx, modem_num=xxx)
cellular_modem.change_modem_bank("2","0")

Your function assumes that, in its global argument space there is an object with these 2 attributes:

args.sim_bank, args.modem_num

You change the function to something like:

def change_modem_bank(bank_num=None, modem=None, args=None):  
    if args and args.sim_bank and args.modem_num:
        bank_num = args.sim_bank
        modem = args.modem_num

and invoke it in the main as:

args.func(args=args)

This way it is clear where the function is getting its args variable from. It also behaves rationally when args is a simple default value like None.

One way or other you need to initialize an args variable when importing, and then write your function is a way that it will be ok with that default version.

Thanks great answer, unfortunately doens't work in my case as then all functions would need at least one argument from args=args and most of them don't have one. Will work it out! — Paul, May 19 '15 at 09:07

call method without args from argparse

2 Answers2