CODEWITHSUNDEEP
pythondictionarytuplespermutation
user2543682
user2543682

Reputation: 353

How to find combinations of a list in a Dictionary?

I am trying to find any permutation of a list inside another Dictionary with tuples.

For example, what would be the best way to find any combination of [1,2,3] inside of a Dictionary which is formatted like this: {(1,3,2):'text',(3,1,2):'text'}.

The only matches that would qualify for [1,2,3] would be (1,2,3),(1,3,2),(2,1,3),(2,3,1),(3,2,1),(3,1,2).

Matches that wouldn't qualify include Lists that don't contain all of the items (For example: (1,2) or (2)), and matches that contain extra items (for example:(1,2,3,4) or (2,3,7,1)).

Upvotes: 0

Views: 72

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1124090

Use itertools.permutations() to generate all permutations of a list:

from itertools import permutations

if any(tuple(perm) in yourdictionary for perm in permutations(yourlist)):
    # match found

but you really want to rethink your data structure. If you made your keys frozenset() objects instead, you simply would test for:

if frozenset(yourlist) in yourdictionary:
    # match found

which would be a lot faster.

Demos:

>>> from itertools import permutations
>>> yourdictionary = {(1,3,2):'text',(3,1,2):'text'}
>>> yourlist = [1, 2, 3]
>>> print any(tuple(perm) in yourdictionary for perm in permutations(yourlist))
True
>>> yourdictionary = {frozenset([1, 2, 3]): 'text', frozenset([4, 5, 6]): 'othertext'}
>>> frozenset(yourlist) in yourdictionary
True
>>> frozenset([2, 3]) in yourdictionary
False

Upvotes: 2

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