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RoyalUp
Asked: 2020-01-12 09:33:29 +0800 CST 2020-01-12 09:33:29 +0800 CST

Count number of positions that match elements of two lists

  • 772

I have two lists of the same length, and I want to count the number of positions in which the elements of both lists match. I've done something like this but I think it doesn't make much sense:

def cuenta_coincidentes(l1,l2):
res=0;
for x in l1:
    for y in l2:
        if l1.index(x)==l2.index(y):
            res+=1;
return res;
python

2 Answers

  1. Best Answer

    A very simple way is the following:

    lista1 = [1, 4, 5, 6, 3]
lista2 = [1, 2, 5, 8, 3]

print(sum(a == b for a, b in zip(lista1, lista2)))

    Being sure that both lists have the same length, we can:

    • With zip(lista1, lista2)we combine each element of the two lists into tuples, that is, like this:(1,1), (4,2), (5,5), (6,8), (3,3)
    • Then we add those that are equal a == b, the Trueis coerced to 1, so the sum will give us the number of matching elements.
    • 4

  2. To know how many times it happens that the element of list1 in position x is equal to the element of list2 in the same position x, then all you have to do is go through both lists at the same time and compare that element.

    def cuenta_coincidentes(l1, l2):
    res = 0
    num_elem = len(l1)
    for x in range(num_elem):
        if l1[x] == l2[x]:
            res += 1
    return res;
    • 3