How to cross-identify elements from multiple lists

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First I apologize if the title question was very vague.

I'll directly move on to explanation for clarifying the question.

Say you have two lists with same length, for example

a = [1,2,3,4,5,6]
b = [3,1,4,2,5,6]

You want to check each index of the list are same or not. So first step would be comparing 1 and 3. Second step would be comparing 2 and 1. One attempt that I tried was using the zip() method, but after the first line:

`for i in zip(a,b):`

I don't think there would be an appropriate line to add for comparing whether each element is equal or not.

Another attempt was:

for i in a:
    for j in b:

and then go on with commands. However, this also has problem since it would be comparing 1,3 and then (1,1), (1,4), (1,2), ... basically comparing 1st element from list a and all elements in b. Then comparing 2nd element in a, and all elements in b.

Could anyone shed some light on how to code the command of comparing each elements with same index from multiple lists?

list arrays python
1 Answers

Here is an answer with python 3 since this seems to be the language you are using.

for i in a iterates over the items in a. What you are looking for is iterate over the indices of its items (from 0 to len(a) - 1):

>>> for i in range(len(a)):
        if a[i] == b[i] : print(i, "=>", a[i])
4 => 5
5 => 6

Python also has some functional programming abilities. Here is a variation with list comprehension:

>>> common_indices = [ i for i in range(len(a)) if a[i] == b[i] ]
>>> for i in common_indices: print(i, "=>", a[i])
4 => 5
5 => 6

Similarly, python has dict comprehension. Here is a variation with dict comprehension:

>>> common_values = { i: a[i] for i in range(len(a)) if a[i] == b[i] }
>>> for i, v in common_values.items(): print(i, "=>", v)
4 => 5
5 => 6
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