Compare two lists A, B in Python find all elements in A which correspond to the same number in B

Question

I want to compare two Python lists, \'A\' and \'B\' in such a manner that I can find all elements in A which correspond to the same number in B

Answer 1

Try this approach.

unique = set(B)    # Creates a set of unique entries in B
for u in unique:
    # Find indices of unique entry u
    indices = [i for i, x in enumerate(B) if x == u]

    # Pull out these indices in A
    corrEntry = [A[i] for i in indices]  

    # Do something with the data, in this case print what OP wants
    print('{} corresponds to the number {} of list B'.format(corrEntry , B[indices[0]]))

It finds the unique entries in B by using the set function. We then loop through these unique entries. The first list comprehension (for indices) finds the indices of the entries in B that match this unique entry. The second saves the value in A of those indices.