How to produce all combinations?

Question

I am trying to make a python program that produces all combinations of an n-1 number with a length L:

I've tried using the itertools but to not avail. I am trying to make it so that it produces the output above when I give it the arguments 5 3 in my terminal. I am using python3. An explanation would be great. Here is my code.

import sys
import itertools

def comb(A,n,k,p,lo):
    stuff = [A, n, k,p,lo]
    return itertools.combinations(stuff, len(stuff)

if __name__ == "__main__":
    d = len(sys.argv)>3
    n = int(sys.argv[1])
    k = int(sys.argv[2])
    A = []
    for i in range(k):
         A.append(0)
    if d: print("n:",n,"k:",k)
    comb(A,n,k,0,0)

It looks like your indentation is off a little and that makes it hard to see what's going on. What is the output you get now? — munk, May 02 '18 at 01:33
where do you print the `comb(A,n,k,0,0)` Why do you have 2 zeroes in the list for `stuff`? Why can't you just to this? `combinations(range(n), L)` where n is your number — Abhishek Dujari, May 02 '18 at 01:34
My bad it looks like it got messed up in the copy over. I'll correct it. — J.Doe, May 02 '18 at 01:34
What is "an n-1 number"? What is a "number with a length L?". — Paul Cornelius, May 02 '18 at 01:34
An n-1 is how it sounds. For example 5 would produce all combos 0-4. L is the length of the combination list. — J.Doe, May 02 '18 at 01:36
"An n-1 number" sounds to me like nonsense. I think you mean that n is the first command line argument to your program, and L is the second command line argument. Then your task is to produce all L-length combinations of integers between 0 and n-1 (inclusive). Is that right? — Paul Cornelius, May 02 '18 at 01:45
It doesn't appear that you've even bothered to read the [`itertools.combination()` documentation](https://docs.python.org/3/library/itertools.html#itertools.combinations). — martineau, May 02 '18 at 02:10

Abhishek Dujari · Answer 1 · 2018-06-12T05:44:43.580

0

print(itertools.combinations(range(int(sys.argv[1])),int(sys.argv[2])))

edited: to intify the input as pointed out

edited Jun 12 '18 at 05:44

answered May 02 '18 at 01:38

Abhishek Dujari

2,343
33
43

It's giving me a compile error. This is how I am trying to implement it. It says str object cannot be used as an integer. def comb(A,n,k,p,lo): print(itertools.combinations(range(sys.argv[1]),sys.argv[2])) – J.Doe May 02 '18 at 01:43
1

You need to convert the arguments to ints - replace with `sys.argv[1]` with `int(sys.argv[1])` and likewise for argv[2]. – Paul Cornelius May 02 '18 at 01:46
Yes sorry I was typing on the phone and get lazy. @Paul Cornelius is correct – Abhishek Dujari May 02 '18 at 07:22

score 0 · Answer 2 · answered May 02 '18 at 01:51

import sys
from itertools import combinations

if __name__ == "__main__":
    d = len(sys.argv)>3
    n = int(sys.argv[1])
    k = int(sys.argv[2])
    A = []
    for i in range(n):
        A.append(i)
    if d: 
        print("n:",n," k:",k)
    val = combinations(A, k)
    for i in val:
        print(i)

You don't need a helper function I don't think

score 0 · Accepted Answer · edited Jun 20 '20 at 09:12

0

This should run with python 3:

test.py

import sys
import itertools

def printArray(inputArray):
  print('[', str(inputArray)[1:-1], ']')

def comb(arr, r):
  output = itertools.combinations(arr, r)
  for x in output:
    printArray(x)

if __name__ == "__main__":
  arr = range(int(sys.argv[1]))
  r = int(sys.argv[2])
  comb(arr, r)

Just use: python3 test.py 5 3

output is:

[ 0, 1, 2 ]
[ 0, 1, 3 ]
[ 0, 1, 4 ]
[ 0, 2, 3 ]
[ 0, 2, 4 ]
[ 0, 3, 4 ]
[ 1, 2, 3 ]
[ 1, 2, 4 ]
[ 1, 3, 4 ]
[ 2, 3, 4 ]

edited Jun 20 '20 at 09:12

Community

1
1

answered May 02 '18 at 01:53

BenD

118
1
10

@ J.Doe Since the result of combinations is an iterable we have to loop through it after in order to print. Additionally, for the first argument we can't just send int(sys.argv[1]) because itertools.combinations expects an iterable to be sent – BenD May 02 '18 at 01:56
my last question is how would you print this out as an array instead of strings. Mainly how do you print [] instead of ()? – J.Doe May 02 '18 at 02:05
I think you could create a little helper function and then for each small array print out a specific format. I'll play around with it and update – BenD May 02 '18 at 02:12
@ J.Doe for python3 you could do the printArray function I've added – BenD May 02 '18 at 02:24
thank you. How would I eliminate the white space on sides? – J.Doe May 02 '18 at 02:27
No problem. For the white spaces you'll probably have to try some things out. You could start at these resources: [print](http://thomas-cokelaer.info/tutorials/python/print.html) and [Similar question](https://stackoverflow.com/questions/11178061/print-list-without-brackets-in-a-single-row) – BenD May 02 '18 at 02:31

How to produce all combinations?

3 Answers3

test.py