CODEWITHSUNDEEP
pythonpython-2.7combinations
Shankar
Shankar

Reputation: 3624

Python fastest method to group pairs from a list of items

As a part of my project, I need to group characters as pairs (unique). I have more than 1000 of these characters in a list. What would be the fastest and optimized method to create unique pairs out of these list of characters. I am using itertools currently and my code seems to perform pretty badly.

My Code using itertools:

import itertools

characters = ['A', 'B', 'C', 'D', 'E']
relations = []
for character in range(len(characters) + 1):
    for combination in itertools.combinations(characters, character):
        if len(combination) == 2:
            relations.append(combination)
print relations

Expected Output: 

[('A', 'B'), ('A', 'C'), ('A', 'D'), ('A', 'E'), ('B', 'C'),   
('B', 'D'), ('B', 'E'), ('C', 'D'), ('C', 'E'), ('D', 'E')]

Upvotes: 1

Views: 271

Answers (1)

Pavel Anossov
Pavel Anossov

Reputation: 62908

All you need are combinations of length 2?

In [48]: characters = ['A', 'B', 'C', 'D', 'E']

In [50]: list(itertools.combinations(characters, 2))
Out[50]:
[('A', 'B'),
 ('A', 'C'),
 ('A', 'D'),
 ('A', 'E'),
 ('B', 'C'),
 ('B', 'D'),
 ('B', 'E'),
 ('C', 'D'),
 ('C', 'E'),
 ('D', 'E')]

You are also generating combinations of length 3 to len(characters) and throwing them all away.

characters = ['A', 'B', 'C', 'D', 'E']
relations = list(itertools.combinations(characters, 2))

Upvotes: 5

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