Create all possible character combinations of any size

Question

I am trying to create all possible character combinations of a given word. For example, “laptop” will include the following possible combinations:

l
la
lap
lapt
lapto
laptop
lp
lpa
lpat
lpato
lpatop

Here is what I have tried:

#!/usr/bin/env python
import argparse
import sys

def parse_args(argv):
    """parsing argument"""
    parser = argparse.ArgumentParser()
    parser.add_argument('-input', dest='input', type = str,
                         required = True,
                         help = "please provide string")
    args = parser.parse_args(argv)
    return args


def get_patt(patt, patt_index, new_pat):
    print new_pat
    for i in range(patt_index, len(patt), 1):
        new_pat = new_pat + patt[i]
        print new_pat
def main(args):
    f_pat = ""
    input = args.input
    for k in range(0, len(input), 1):
        for i in range(0, len(input), 1):
            f_pat =  input[i]
            for j in range(i+1, len(input), 1):
                f_pat = f_pat + input[j]
                get_patt(input, j+1, f_pat)
        input = args.input[k:] + args.input[:k]
        print "Input String", input

if __name__ == "__main__":
    args =parse_args(sys.argv[1:])
    main(args)

Answer 1

Improvements

1. Use either argparse or sys.argv because this feels just wierd, and kind of surprised it worked at all. I'd recommend sticking with argparse
2. Secondly, be sure to check out the itertools module from python, because what you are looking for are basicly permutations of a word.

---

New code

import argparse
from itertools import permutations


def main(string):
    for idx in range(1, len(string)+1):
        print(list(''.join(p) for p in permutations(string, idx)))


def parse_args():
    """parsing argument"""
    parser = argparse.ArgumentParser()
    parser.add_argument('-input', dest='input', type = str,
                         required = True,
                         help = "please provide string")
    return parser.parse_args()


if __name__ == "__main__":
    args = parse_args()
    main(args.input)

Answer 2

Your arguments parsing is a bit off.

If you remove the - in front of the name of the argument, argparse will consider it a required parameter and not an optional one, so you won't have to specify required=True.

Besides, removing it will make the help look cleaner as regard to the fact that the parameter is required:

$ python2 combinations.py -h
usage: combinations.py [-h] input

positional arguments:
  input       please provide string

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

You could also return the word from your parse_args function so the main is agnostic of how you provide your input.

Lastly, a parser's parse_args method, if called without arguments, will automatically take sys.argv[1:] as the reference. So you don't need to specify it yourself:

def parse_args():
    """parsing argument"""
    parser = argparse.ArgumentParser()
    parser.add_argument('input', help='please provide string')
    args = parser.parse_args()
    return args.input


def main(word):
    ...


if __name__ == '__main__':
    main(parse_args())