Understanding python's argparse module

Question

I am trying to work with argparse in python and I do not know how to call the program at command line to see if it works.

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("DocID", type= int, help= "Insert DocID Here")
parser.add_argument("echo", help = "Enter in the FileName to be read")
args = parser.parse_args()
print args

This is my incredibly basic program that I am trying to use just to learn more about how argparse works. I just need to learn how and where to call the program to be able to use the arguments I give it.

Edit: To make my question more clear sorry. I have this code, but I do not know how to call the program as a whole so that I can run it. Like how would I run this in command line? Because when run just in IDLE it produces and error because of a lack of commands

What are you trying to do? Have you read that?

Pierre GM
– Pierre GM

2012-08-28 14:15:22 +00:00
Commented Aug 28, 2012 at 14:15 — Pierre GM
– Pierre GM, Commented Aug 28, 2012 at 14:15
Argument names are usually preceded by a '--' or a '-'.

squiguy
– squiguy

2012-08-28 14:16:17 +00:00
Commented Aug 28, 2012 at 14:16 — squiguy
– squiguy, Commented Aug 28, 2012 at 14:16

mgilson · Accepted Answer · 2012-08-28 14:26:38Z

4

an ArgumentParser's parse_args method can take a list as input. That list is used for parsing the commandline arguments. So, a common idiom is:

args = parser.parse_args('-a -b -c --value=True'.split())

since str.split returns a list. ('a b c'.split() == ['a', 'b', 'c'])

Usually when you add arguments, you do so like this:

parser.add_argument('-a', '--a-long-name', type=int, ...)

Arguments without a - or -- in front are positional arguments, so both of your arguments are positional. You can see a little of what is happening if you do:

args = parser.parse_args(['1','foo'])
print args.DocID # 1
print args.echo  # foo

which is the same as calling your script as python youscript.py 1 foo (without the list inside parse_args).

edited Aug 28, 2012 at 14:26

answered Aug 28, 2012 at 14:17

mgilson

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2 Comments

user1614796 Over a year ago

How can I make the script 'python youscript.py arg1 arg 2' work though. This is my real issue, that I get the python is not recognized as a command error

mgilson Over a year ago

Then it seems that you have python installed in a non-standard place (outside of path). What OS are you using? If on *NIX, try the path to python pointed to by idle. In other words, head $(which idle) will have a path to python coded into the first line. try that path.

gbin · Accepted Answer · 2012-08-28 14:37:34Z

0

If you want to know the command line syntax of the script... just call it with --help, argparse automatically provides it for you.

⚫  gbin@sal tmp % python test.py --help
usage: test.py [-h] DocID echo

positional arguments:
  DocID       Insert DocID Here
  echo        Enter in the FileName to be read

optional arguments:
  -h, --help  show this help message and exit

answered Aug 28, 2012 at 14:37

gbin

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