Use argparse module in python to parse a single argument

Question

I used the OptParse module a few years back, and it seemed so easy, but seeing the argparse module, it doesn't seem intuitive to use. Thus, I'd like some help.

I currently have (which isnt much yet):

import argparse
parser = argparse.ArgumentParser()
parser.parse_args()

I'd like to be able to issue a command like python myscript.py --char 20 . This value for char flag will always be an int.

If someone can please help, I'd greatly appreciate it! Thank you

Have you considered adding the argument you want to take to the parser? What's the problem? — jonrsharpe
– jonrsharpe, Commented Nov 19, 2015 at 0:54
I think a quick Google search answers this question the best. — Totem
– Totem, Commented Nov 19, 2015 at 0:56
This task isn't significantly different between optparse and argparse. — chepner
– chepner, Commented Nov 19, 2015 at 2:15

Totem · Accepted Answer · 2015-11-19 00:49:56Z

2

This is how you add an argument, and retrieve it:

import argparse
parser = argparse.ArgumentParser()

parser.add_argument('--char', type=int,
                   help='number of characters')

args = parser.parse_args()
char = args.char

You should check out the docs: https://docs.python.org/3/library/argparse.html

And here's a tutorial: https://docs.python.org/2/howto/argparse.html

answered Nov 19, 2015 at 0:49

Totem

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1 Comment

hpaulj Over a year ago

There's a section at the end of the argparse docs about translating optparse to argparse.

Haleemur Ali · Accepted Answer · 2015-11-19 00:50:11Z

1

you need to add an argument to the parser object, and optionally specify the parameter type to be int

# testargs.py
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--char', type=int)
args = parser.parse_args()

print(args.char)

if you execute this file with

python testargs.py --char 20

it should print 20 to the console

answered Nov 19, 2015 at 0:50

Haleemur Ali

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1 Comment

hpaulj Over a year ago

Just a point of caution: type=int means, "use the int() function to convert the string to a number". This expression is similar to, but not quite the same as the optparse parser.add_option("-n", type="int", dest="num").

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