From given three array find the duplicates which have same attributes in all the three arrays.

Question

It runs fine but it prints 1 more if more than one duplicate is present.
https://code.sololearn.com/cq6PI2W1T5bP/?ref=app

Answer 1

print(len(l1)-len(set([tuple(i) for i in l1])))

Answer 2

Thanks it work. But can you explain that?

Answer 3

Ok thanks. Why should I convert it to tuple. Why It shows error when I use len(set(l1))

Answer 4

In simple terms, lists can't be used inside sets, but tuples can.

Answer 5

[tuple(i) for i in l1] converts every element of l1 into a tuple.
[[1, 2], [3, 4]] -> [(1, 2), (3, 4)]

set(...) removes all duplicates (it can do much more than that).

len(l1)-len(set(...)) returns the total number of items minus the number of unique items, resulting in the number of duplicate items.