Tell me more ×
Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free, no registration required.
up vote 0 down vote favorite

I am making a basic calculator using argparse. I basically accept some numbers from the command line followed by either add,subtract,multiply,or divide action. I only have the adding part right now. Here is my code:

import argparse
from sys import argv

def get_args(args):
    parser = argparse.ArgumentParser(description = 'Calculator')
    parser.add_argument('integers', metavar='N', type=int, nargs='+',
           help='an integer for the accumulator')
    parser.add_argument('--add',dest = 'sum',help = "Adds the set of numbers")
    parser.add_argument('--subtract', 
                    help = "Subtracts the set of numbers")
    args = parser.parse_args()

def main(argv):
    args = get_args(argv[0:])
    if args.a or args.add:
        return sum(args)

if __name__ == "__main__":main(argv)

However, when i input:

calculator.py 1 2 3 --add

it gives me the error: expected one argument and also, in python there is a function sum(), but is there a subtract,multiply,and divide function as well? If not, then how do i return the sum without using the sum() function. I assume you would use a for loop to cycle through all the numbers?

So using the for loop would be something like this:

def main:
    args = get_args(argv[0:])
    if args.a or args.add:
        for row in argv[1:]:
            sum = sum + argv[row]
        print sum
share|improve this question
add comment (requires an account with 50 reputation)

1 Answer

up vote 2 down vote accepted

Your --add command-line switch wants to have an argument. Make it a switch instead:

parser.add_argument('--add', action='store_true', help="Adds the set of numbers")

Note that I removed the dest argument, you want the result to be stored in args.add, not args.sum.

Your get_args() function needs to return the result of parser.parse_args():

def get_args(args):
    # ....
    return parser.parse_args()

There won't be a args.a, just test for args.add only, and you want to sum the args. integers attribute, not the args namespace object itself. You probably wanted to print the result:

if args.add:
    print sum(args.integers)

If you wanted to use a loop instead, loop over args.integers:

if args.add:
    result = 0
    for value in arg.integers:
        result += value
    print result
share|improve this answer
Yes, but then there is another error: 'Nonetype' object has no attribute 'add' – Andy Jul 24 at 15:52
@Andy: Read the rest of my answer. You had multiple errors in your program. – Martijn Pieters Jul 24 at 15:53
Thanks a lot, works!! – Andy Jul 24 at 15:58
Glad to have been of help! Feel free to accept my answer if you feel it was useful to you. :-) – Martijn Pieters Jul 24 at 16:06
add comment (requires an account with 50 reputation)

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.