Python Command Args

Question

I have been googling almost an hour and am just stuck.

for a script, stupidadder.py, that adds 2 to the command arg.

e.g. python stupidadder.py 4

prints 6

python stupidadder.py 12

prints 14

I have googled so far:

import argparse parser = argparse.ArgumentParser(description='Process some integers.') parser.add_argument('x', metavar='x', type=int, nargs='+',                     help='input number')  ...  args = parser.parse_args() print args x = args['x']  # fails here, not sure what to put print x + 2 

I can't find a straightforward answer to this anywhere. the documentation is so confusing. :( Can someone help? Please and thank you. :)

Answer 1

Assuming that you are learning how to use the argparse module, you are very close. The parameter is an attribute of the returned args object and is referenced as x = args.x.

import argparse parser = argparse.ArgumentParser(description='Process some integers.') parser.add_argument('x', metavar='x', type=int, nargs='+',                     help='input number')  ...  args = parser.parse_args() print args #x = args['x']  # fails here, not sure what to put x = args.x print x + 2 

Answer 2

A sample run in Ipython with your code, showing that args is a simple object, not a dictionary. In the argparse code the namespace is accessed with getattr and setattr

In [4]: args=parser.parse_args(['12','4','5']) In [5]: args Out[5]: Namespace(x=[12, 4, 5]) In [6]: args['x'] --------------------------------------------------------------------------- TypeError                                 Traceback (most recent call last) <ipython-input-6-3867439e1f91> in <module>() ----> 1 args['x'] TypeError: 'Namespace' object is not subscriptable In [7]: args.x Out[7]: [12, 4, 5] In [8]: getattr(args,'x') Out[8]: [12, 4, 5] In [9]: sum(getattr(args,'x')) Out[9]: 21 

vars() can be used to turn the namespace into a dictionary.

In [12]: vars(args)['x'] Out[12]: [12, 4, 5] 

Review the Namespace section of the argparse documentation.