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 loop through list with do something
I have to do something with all combinations in a list.

Initial thought
itertools.combinations(mylist, 2)

But I have to something with the values of mylist and computing them over and over seems not logical.

def myfunct(a)
	#do something with a
	#return something

mylist = [1,2,3,4,5]

for index, item in enumerate(mylist):
	val = myfunct(item)
	for i in mylist[index+1:]:
		# do something with 'val' and with i
so in my example I only have to calculate 'val' once for each loop

my thought is doing this with itertools I have to calculate val for each item everytime.

Brainfart or could I do this better?
If the items in mylist are hashable, you could use functools.lru_cache
from functools import lru_cache
import itertools as itt

def myfunct(a):
    #do something with a
    #return something

myf = lru_cache()(myfunct)
mylist = [1,2,3,4,5]

for x, y in itt.combinations(mylist, 2):
    val = myf(x)
    print(x, y)
myfunct(1) 1 2 1 3 1 4 1 5 myfunct(2) 2 3 2 4 2 5 myfunct(3) 3 4 3 5 myfunct(4) 4 5

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