CODEWITHSUNDEEP
pythonperformancelist
Fernando Barraza
Fernando Barraza

Reputation: 137

fastest way to combine two huge list of tuples in python

I have two list like these:

L1 = [(1, 'a'), (2, 'm'), (3, 'd') ....] 
L2 = [('b', 1), ('f', 2), ('x', 1), ('w', 3), ('j', 2) ... ]

and I want to produce:

L3 = [('a','b'),('m','f'),('a','x'),('d','w'),('m','j'), ...]

I mean, where second element in tuple of list L1 match with first element in tuple of list L2.

L1 and L2 are above 12 millions of tuples.

I have a code that works using nested loops for comparison between 'keys' of each tuples but is fairly inefficient.

What could be a good alternative to do it in the faster way ?

Thank you in advance.

Upvotes: 2

Views: 636

Answers (1)

Marat
Marat

Reputation: 15738

dictionaries have O(1) select/insert complexity. Use them:

L1_dict = dict(L1)
L3 = [(L1_dict[k], v) for v, k in L2 if k in L1_dict]

Upvotes: 5

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