CODEWITHSUNDEEP
pythoniterationcombinations
user3077008
user3077008

Reputation: 847

Two Combination Lists from One List

I am a python beginner. I am trying to get two combination lists from one list.

For example, I have a list:

c = [1, 2, 3, 4]

I want to get every possible combination using every four items to fill two lists. There are going to be ((2^4)/2)-1 possibilities.

c1 = [1]  c2 = [2, 3, 4]
c1 = [2]  c2 = [1, 3, 4]
c1 = [3]  c2 = [2, 3, 4]
c1 = [4]  c2 = [1, 2, 3]
c1 = [1, 2]  c2 = [3, 4]
c1 = [1, 3]  c2 = [2, 4]
c1 = [1, 4]  c2 = [2, 3]

The function usually works for this kind of task is itertools, but I cannot choose the number of lists produced by itertools.combination.

The function only allows me to choose how many items per one list should be.

For example, If I try following function,

print list(itertools.combinations(c, 2))

I can get an outcome only like this.

[(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)]

I searched pretty hard to find this, but I couldn't find anything.

Update

Oh my poor English is causing such a confusion! I totally changed my example. I wanted to allocate the 4 items to 2 lists. Sorry for the confusion!

Upvotes: 4

Views: 185

Answers (2)

hjpotter92
hjpotter92

Reputation: 80657

I'm unsure as to what your understanding of 10 choose 2 is. The output you receive from list(itertools.combinations(c, 2)) is what is mathematically defined as 10C2.

EDIT

From the edit to your question, it appears that you want an entirely different kind of combinations. The number of outcomes would still not be 45, but instead: 10C1 + 10C2 + 10C3 + 10C4 + 10C5.

I expect the following should help you move forward:

for i in range(1, 6):
    for c1 in itertools.combinations(c, i):
            c1 = set(c1)
            c2 = set(c) - c1
            print c1, c2

The above code was inspired by this (deleted) answer by CSZ.

The output received when range(1, 3) is used:

[1] [2, 3, 4, 5, 6, 7, 8, 9, 10]
[2] [1, 3, 4, 5, 6, 7, 8, 9, 10]
[3] [1, 2, 4, 5, 6, 7, 8, 9, 10]
[4] [1, 2, 3, 5, 6, 7, 8, 9, 10]
[5] [1, 2, 3, 4, 6, 7, 8, 9, 10]
[6] [1, 2, 3, 4, 5, 7, 8, 9, 10]
[7] [1, 2, 3, 4, 5, 6, 8, 9, 10]
[8] [1, 2, 3, 4, 5, 6, 7, 9, 10]
[9] [1, 2, 3, 4, 5, 6, 7, 8, 10]
[10] [1, 2, 3, 4, 5, 6, 7, 8, 9]
[1, 2] [3, 4, 5, 6, 7, 8, 9, 10]
[1, 3] [2, 4, 5, 6, 7, 8, 9, 10]
[1, 4] [2, 3, 5, 6, 7, 8, 9, 10]
[1, 5] [2, 3, 4, 6, 7, 8, 9, 10]
[1, 6] [2, 3, 4, 5, 7, 8, 9, 10]
[1, 7] [2, 3, 4, 5, 6, 8, 9, 10]
[8, 1] [2, 3, 4, 5, 6, 7, 9, 10]
[1, 9] [2, 3, 4, 5, 6, 7, 8, 10]
[1, 10] [2, 3, 4, 5, 6, 7, 8, 9]
[2, 3] [1, 4, 5, 6, 7, 8, 9, 10]
[2, 4] [1, 3, 5, 6, 7, 8, 9, 10]
[2, 5] [1, 3, 4, 6, 7, 8, 9, 10]
[2, 6] [1, 3, 4, 5, 7, 8, 9, 10]
[2, 7] [1, 3, 4, 5, 6, 8, 9, 10]
[8, 2] [1, 3, 4, 5, 6, 7, 9, 10]
[9, 2] [1, 3, 4, 5, 6, 7, 8, 10]
[2, 10] [1, 3, 4, 5, 6, 7, 8, 9]
[3, 4] [1, 2, 5, 6, 7, 8, 9, 10]
[3, 5] [1, 2, 4, 6, 7, 8, 9, 10]
[3, 6] [1, 2, 4, 5, 7, 8, 9, 10]
[3, 7] [1, 2, 4, 5, 6, 8, 9, 10]
[8, 3] [1, 2, 4, 5, 6, 7, 9, 10]
[9, 3] [1, 2, 4, 5, 6, 7, 8, 10]
[10, 3] [1, 2, 4, 5, 6, 7, 8, 9]
[4, 5] [1, 2, 3, 6, 7, 8, 9, 10]
[4, 6] [1, 2, 3, 5, 7, 8, 9, 10]
[4, 7] [1, 2, 3, 5, 6, 8, 9, 10]
[8, 4] [1, 2, 3, 5, 6, 7, 9, 10]
[9, 4] [1, 2, 3, 5, 6, 7, 8, 10]
[10, 4] [1, 2, 3, 5, 6, 7, 8, 9]
[5, 6] [1, 2, 3, 4, 7, 8, 9, 10]
[5, 7] [1, 2, 3, 4, 6, 8, 9, 10]
[8, 5] [1, 2, 3, 4, 6, 7, 9, 10]
[9, 5] [1, 2, 3, 4, 6, 7, 8, 10]
[10, 5] [1, 2, 3, 4, 6, 7, 8, 9]
[6, 7] [1, 2, 3, 4, 5, 8, 9, 10]
[8, 6] [1, 2, 3, 4, 5, 7, 9, 10]
[9, 6] [1, 2, 3, 4, 5, 7, 8, 10]
[10, 6] [1, 2, 3, 4, 5, 7, 8, 9]
[8, 7] [1, 2, 3, 4, 5, 6, 9, 10]
[9, 7] [1, 2, 3, 4, 5, 6, 8, 10]
[10, 7] [1, 2, 3, 4, 5, 6, 8, 9]
[8, 9] [1, 2, 3, 4, 5, 6, 7, 10]
[8, 10] [1, 2, 3, 4, 5, 6, 7, 9]
[9, 10] [1, 2, 3, 4, 5, 6, 7, 8]

Upvotes: 3

huang
huang

Reputation: 519

l = [1,2,3,4, 5,  6, 7, 8]

print [[l[:i], l[i:]] for i in range(1, len(l))]

If you want all combinations. you can do like this.

print [l[i:i+n] for i in range(len(l)) for n in range(1, len(l)-i+1)]

or

itertools.combinations

Upvotes: 2

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