CODEWITHSUNDEEP
pythonlist
H. Wilde
H. Wilde

Reputation: 197

How to get all pairs from a list that fulfil some condition in Python

I am trying to generate a list of ordered pairs with replacement (i.e. needs (0.1, 0.1), (0.1, 0.2) and (0.2, 0.1))that fulfil the condition that their sum is <= max_sum in Python. For example, given max_sum=1 and the list:

[0, 0.1, 0.2, ..., 0.9, 1.0]

I'd like to produce a list containing:

[(0, 0), (0, 0.1), ..., (0, 0.9), (0, 1.0), (0.1, 0), (0.1, 0.1), ..., (0.1, 0.8), (0.1, 0.9), (0.2, 0), (0.2, 0.1), ...]

but not (0.1, 1.0) etc.

Here is a likely inefficient and ugly solution that has some issues in that the if statement sometimes doesn't resolve correctly:

alphas = [0., .1, .2, .3, .4, .5, .6, .7, .8, .9, 1.]
max_sum = 1
def get_pairs(alphas, max_sum)
    for a in alphas:
        for b in alphas:
            if a + b <= max_sum:
                yield (a, b)

Upvotes: 1

Views: 1134

Answers (3)

jawsem
jawsem

Reputation: 771

You can use itertools permutations. Example code.

from itertools import permutations


test_list = [0, 0.1, 0.2, 0.9, 1.0]
final_list = [item for item in permutations(test_list,2) if sum(item)<=1]
print(final_list)

[(0, 0.1), (0, 0.2), (0, 0.9), (0, 1.0), (0.1, 0), (0.1, 0.2), (0.1, 0.9), (0.2, 0), (0.2, 0.1), (0.9, 0), (0.9, 0.1), (1.0, 0)]

Upvotes: 1

Phoenixo
Phoenixo

Reputation: 2133

If order matters, which means you will have both (0, 0.2) and (0.2,0) for example, then you can try this :

L = [round(x*0.1, 2) for x in range(0, 10)]
print([(x,y) for x in L for y in L if x + y <= 1])

Output :

[(0.0, 0.0), (0.0, 0.1), (0.0, 0.2), ... (0.8, 0.2), (0.9, 0.0), (0.9, 0.1)]

Upvotes: 3

OD1995
OD1995

Reputation: 1777

Something like this:

import itertools
everyPermutation = [x for x in itertools.permutations(iterable, 2)]
finalList = [[x,y] for x,y in everyPermutation if (x + y) <= 1]

Upvotes: 1

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