CODEWITHSUNDEEP
pythoncombinations
user15795580
user15795580

Reputation:

How to make combinations faster in python

I am writing a code in python in which I need all possible combinations of up to 1000 elements and then perform multiple actions on them. Is there any way to reduce the run time. By using itertools the run time is in minutes after just 50 elements. Currently I am using this code (I have commented out the print statement because it significantly increases the run time):

import itertools
import time

def all_combos_func(arguments):
    data = list(arguments)
    return itertools.chain.from_iterable(itertools.combinations(data, r) for r in range(len(data)+1))

start_time = time.time()

all_comb= []
for i in range (1000):
    all_comb.append(i+1)
all_combos = all_combos_func(all_comb)
all_combos_count = []
for i in all_combos:
    all_combos_count.append(i)
    # print(i)
print("this is the total length", len(all_combos_count))
end_time = time.time()

print(end_time-start_time)

Upvotes: 0

Views: 412

Answers (1)

Woodford
Woodford

Reputation: 4439

>>> len(all_combos_func(range(0))
1
>>> len(all_combos_func(range(1))
2
>>> len(all_combos_func(range(2))
4
>>> len(all_combos_func(range(3))
8
>>> len(all_combos_func(range(4))
16

Your all_combos_func is returning 2^(len(input)) combinations. So when you ask for all combinations and you pass in a 1000 element list, you get back 2^1000 results. Yeah, it's gonna take a while.

2^1000 = 10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376

Upvotes: 1

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