How do work 'set' to delete duplicated value in python?

Question

As you know, set, one of the Arrays in python, can delete duplicated value.

like this

thisset = {"apple", "banana", "cherry", "apple"}

to

thisset = {"apple", "banana", "cherry"}

The wondering thing is 'How do set can do this?'

Has set a loop about every each value for finding whether it has duplicated value?

this way looks so inefficient. So I think is's wrong.

I want to know the delete process. Please answer me.

I search it useing my question title, but I could see only about to delete in 'list'.