[Python] Generating all length-N combinations of all length-M sublists of a list, without...

I have a long input list, and I want to generate combinations of 3 elements. But each combination's elements should be drawn from a length-5 sublist of the original list, rather than drawing elements from the whole list.

Equivalently, no two elements of a combination can be spaced more than 4 positions apart in the original list.

I wrote this code:

import itertools

input = [
'a','b','c','d','e','f','g','h','i','j'
]
l=0
space = ' '
count = 3
run = 5

def combine_list(input_list, count, run):
list_out = []
j=0
k = (len(input)-run)+1
while j < k:
comb_set = input_list[j:run+j:]
comb = itertools.combinations(comb_set,count)
for i in comb:
out = space.join(list(i))
list_out += [out]
j += 1
return list_out

x = combine_list(input,count, run)

print(x, len(x))


with this output:

['a b c', 'a b d', 'a b e', 'a c d', 'a c e', 'a d e', 'b c d', 'b c e', 'b d e', 'c d e', 'b c d', 'b c e', 'b c f', 'b d e', 'b d f', 'b e f', 'c d e', 'c d f', 'c e f', 'd e f', 'c d e', 'c d f', 'c d g', 'c e f', 'c e g', 'c f g', 'd e f', 'd e g', 'd f g', 'e f g', 'd e f', 'd e g', 'd e h', 'd f g', 'd f h', 'd g h', 'e f g', 'e f h', 'e g h', 'f g h', 'e f g', 'e f h', 'e f i', 'e g h', 'e g i', 'e h i', 'f g h', 'f g i', 'f h i', 'g h i', 'f g h', 'f g i', 'f g j', 'f h i', 'f h j', 'f i j', 'g h i', 'g h j', 'g i j', 'h i j'] 60


But this produces duplicates. I can sort to remove them, but I would rather not make them in the first place.

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