How to Make A Combination of Lists of A List in Python

Question

I do not know whether to call it combination or permutation, so the question can be edited regarding your comment in question.

I have a list as below:

[
    ["a"],
    ["b", "c"],
    ["d", "e", "f"]
]

I want this to output as:

[
    "abd",
    "acd",
    "abe",
    "ace",
    "abf",
    "acf"
]

My first priority is to make this with built-in tools or by hand, not with other scientific modules. However, if there is no way, scientific modules might be used.

Environment

python 3.5.1

Did you try [`itertools.product`](https://docs.python.org/3.5/library/itertools.html#itertools.product)? — MisterMiyagi, Jul 06 '16 at 08:41

Bhavana · Accepted Answer · 2016-07-06T15:37:27.247

1

As suggested by the comments, you could use itertools.product. Or you could implement a simple recursive method:

def combine(lists, index=0, combination=""):
    if index == len(lists):
        print combination
        return
    for i in lists[index]:
        combine(lists, index+1, combination + i)

lists = [
    ["a"],
    ["b", "c"],
    ["d", "e", "f"]
]

combine(lists)

edited Jul 06 '16 at 15:37

answered Jul 06 '16 at 08:45

Bhavana

311
2
12

You could do this, but why re-invent the wheel? This is a classic `itertools.product` problem. – PM 2Ring Jul 06 '16 at 09:04

How to Make A Combination of Lists of A List in Python

Environment

1 Answers1