Question

Why is the size of sets in Python noticeably larger than that of lists with same elements?

a = set(range(10000))
b = list(range(10000))
print('set size = ', a.__sizeof__())
print('list size = ', b.__sizeof__())

output:

set size = 524488
list size = 90088

Answer 1

The set uses more memory than the list as it stores a table of hashes of all the elements so it can quickly detect duplicate entries and so on. This is why every set member must be hashable.