Ordering by index in pyhton

Question

I have 3 list like

A = [3,8,10,25] B = [14,15,30,23] C = [24,27,31,34]

I need to combine these 3 lists, then sort them and create 3 lists again with their indexes in python

A = [1,2,3,8] B = [4,5,9,6] C = [7,10,11,12]

Answer 1

This is a confusing question. However, I think I have found an answer. What you need to do is first create a second, sorted list that combines A, B and C. Then, you need to check where every item in the list goes in the combined list, if that makes sense.

Try this:

A = [3,8,10,25]
B = [14,15,30,23]
C = [24,27,31,34]

combined = sorted(A + B + C)
print(combined)

a = []
b = []
c = []

def order(origin_lst, new_lst):
    for i in origin_lst:
        new_lst.append(combined.index(i) + 1)
    return new_lst

a = order(A, a)
b = order(B, b)
c = order(C, c)

print(a, b, c)

You get an output of: [1, 2, 3, 8] [4, 5, 10, 6] [7, 9, 11, 12] which looks right to me.

Answer 2

Merge the lists into a flat one, reordering, get the index and regrouping with a slice.

A = [3,8,10,25]
B = [14,15,30,23]
C = [24,27,31,34]

flat = sum((A, B, C), [])
ordered = sorted(flat)
indeces = [ordered.index(i)+1 for i in flat]
A, B, C = [indeces[len(A)*i: len(A)*(i+1)] for i in range(len(flat)//len(A))]

Remark: list.index-based methods are not reliable if the there are repeated values among the lists since it returns the first occurrence.