I have small brain fade today and I believe it will be faster to get hint here than wondering for an hour.

I have list A of 100 elements. How can I create another list(B) basing on list A, that will have 10 elements, so that each element is mean of 10 elements from list A?

Thank you in advance.

e.g.A = [10,10,10,10,10,20,20,20,20,20,30,30,30,30,30,40,40,40,40,40]
B = [15, 35]

A = [i for i in range(100)]
[sum(A[k * 10 : 10*(k+1)])/10 for k in range(len(A)//10)]

Output

[4.5, 14.5, 24.5, 34.5, 44.5, 54.5, 64.5, 74.5, 84.5, 94.5]