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pythoncombinations

Reputation: 1036

python list all combiniations without itertools

I just want to make all combination of list(two size)
for example: input= [1, 2, 3] => output = [[1,2], [1,3], [2,3]]
how can i make this code more concise and simple?(one-liner?)
it doesn't mean list compreshension.

my code

def all_combinations(input_lst):
    return_lst=[]
    for i in range(0, len(input_lst)-1):
        for j in range(i+1, len(input_lst)):
            return_lst.append([input_lst[i], input_lst[j]])
    return return_lst

Upvotes: 0

Views: 690

Answers (2)

Ho0ony

Reputation: 158

l = [1,2,3,4,]
=> [(2, 1), (3, 1), (4, 1), (3, 2), (4, 2), (4, 3)]

1. use enumerate

[ (x,y) for (i,y) in enumerate(l)  for x in l[i+1:] ]

2. use index

[ (x,y) for y in l  for x in l[l.index(y)+1:] ]

Upvotes: 0

Reputation: 1416

[(input_lst[i], input_lst[j]) for i in xrange(len(input_lst) - 1) for j in xrange(i + 1, len(input_lst))]

Upvotes: 2

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