Problem:

• I have a list of elements without repetitions (a set, basically);
• I would like to have a list of all their combinations of length L containing no more than r repetitions of each element.

What would be the best pythonic way to accomplish this?

Probably some adjustments to this answer could be made?..

CodePudding user response：

You can use the itertools.combinations_with_replacement and then filter out the ones with too many repeated elements using the collections.Counter.

from itertools import combinations_with_replacement
from collections import Counter

a = ["h","e","l","o","w","r","d"]
L, r = 3, 2
result = []

for combo in combinations_with_replacement(a, L):
    tally = Counter(combo)
    if max(tally.values()) <= r:
        result.append(combo)

print(result)

OUTPUT

[('h', 'h', 'e'), ('h', 'h', 'l'), ('h', 'h', 'o'), ('h', 'h', 'w'), ('h', 'h', 'r'), ('h', 'h', 'd'), ('h', 'e', 'e'), ('h', 'e', 'l'), ('h', 'e', 'o'), ('h', 'e', 'w'), ('h', 'e', 'r'), ('h', 'e', 'd'),
 ('h', 'l', 'l'), ('h', 'l', 'o'), ('h', 'l', 'w'), ('h', 'l', 'r'), ('h', 'l', 'd'), ('h', 'o', 'o'), ('h', 'o', 'w'), ('h', 'o', 'r'), ('h', 'o', 'd'), ('h', 'w', 'w'), ('h', 'w', 'r'), ('h', 'w', 'd'),
 ('h', 'r', 'r'), ('h', 'r', 'd'), ('h', 'd', 'd'), ('e', 'e', 'l'), ('e', 'e', 'o'), ('e', 'e', 'w'), ('e', 'e', 'r'), ('e', 'e', 'd'), ('e', 'l', 'l'), ('e', 'l', 'o'), ('e', 'l', 'w'), ('e', 'l', 'r'),
 ('e', 'l', 'd'), ('e', 'o', 'o'), ('e', 'o', 'w'), ('e', 'o', 'r'), ('e', 'o', 'd'), ('e', 'w', 'w'), ('e', 'w', 'r'), ('e', 'w', 'd'), ('e', 'r', 'r'), ('e', 'r', 'd'), ('e', 'd', 'd'), ('l', 'l', 'o'),
 ('l', 'l', 'w'), ('l', 'l', 'r'), ('l', 'l', 'd'), ('l', 'o', 'o'), ('l', 'o', 'w'), ('l', 'o', 'r'), ('l', 'o', 'd'), ('l', 'w', 'w'), ('l', 'w', 'r'), ('l', 'w', 'd'), ('l', 'r', 'r'), ('l', 'r', 'd'),
 ('l', 'd', 'd'), ('o', 'o', 'w'), ('o', 'o', 'r'), ('o', 'o', 'd'), ('o', 'w', 'w'), ('o', 'w', 'r'), ('o', 'w', 'd'), ('o', 'r', 'r'), ('o', 'r', 'd'), ('o', 'd', 'd'), ('w', 'w', 'r'), ('w', 'w', 'd'),
 ('w', 'r', 'r'), ('w', 'r', 'd'), ('w', 'd', 'd'), ('r', 'r', 'd'), ('r', 'd', 'd')]

CodePudding user response：

Look at combinations_with_replacement() in itertools

import itertools
for combination in itertools.combinations_with_replacement(['red', 'green', 'blue', 'yellow'], r=3):
     print(combination)

('red', 'red', 'red')
('red', 'red', 'green')
('red', 'red', 'blue')
('red', 'red', 'yellow')
('red', 'green', 'green')
('red', 'green', 'blue')
('red', 'green', 'yellow')
('red', 'blue', 'blue')
('red', 'blue', 'yellow')
('red', 'yellow', 'yellow')
('green', 'green', 'green')
('green', 'green', 'blue')
('green', 'green', 'yellow')
('green', 'blue', 'blue')
('green', 'blue', 'yellow')
('green', 'yellow', 'yellow')
('blue', 'blue', 'blue')
('blue', 'blue', 'yellow')
('blue', 'yellow', 'yellow')
('yellow', 'yellow', 'yellow')
>>>