Finding combinations of list of items (30 or so)

[deanhystad]

All possible combinations of 30 items does take a while to compute. It is funny that you expect to print the output.

from itertools import combinations

items = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')[:4]
combos = sum([list(map(list, combinations(items, i+1))) for i in range(len(items))], [])
if len(combos) < 30:
    print(combos)
else:
    print(len(items), len(combos))

Output:
[['A'], ['B'], ['C'], ['D'], ['A', 'B'], ['A', 'C'], ['A', 'D'], ['B', 'C'], ['B', 'D'], ['C', 'D'], ['A', 'B', 'C'], ['A', 'B', 'D'], ['A', 'C', 'D'], ['B', 'C', 'D'], ['A', 'B', 'C', 'D']]

When I bump the number of items to 10, 15, 20

10 1023
15 32767
20 1048575
30 1073741823

The number of combinations = 2**num_items - 1.

The time for computing the combinations of 20 items is about 2 seconds on my laptop. If the item count is 30, the number of combinations is 1024 times greater, and I would expect it to take about 2048 seconds to compute.