The implementation of list subtraction in Python is described

Problem description: So let's say I have two lists like this,

                  One is list1, list1 = [1, 2, 3, 4, 5]
                  One is list2, list2 = [1, 4, 5]
                  How do we get a new list, list3,
                  List3 contains all the elements in list1 that do not appear in list2.
                  List3 = list1 and list2
                 
Solutions: We can use set operations
                  List3 = list(set(list1) wok (list2))
                 
                  The set operation converts a list into a collection.
                  Suppose: list_t = [1, 2, 3, 1]
                  Then: list(set(list_t)) = [1, 2, 3]
                  Yes, duplicate items will be deleted.

Other options: List3 = [I for I in list1 if I not in list2]             # can be used for list sharding
                  It's also intuitive to write it this way.
                  But when the list is large, it's not as fast as the set method.

Additional knowledge: A = [[I,j] for I in range(2) for j in range(3)]
                  This is very similar to the other plan,
                  It's all judgment and calculation in [].
                  It feels convenient, at least more convenient and faster than the following:
                  A = []
                  For I in range (2) :
                          For j in range (3) :
                                  A.a ppend ([I, j])

Some questions: If list_tmp = [[1,2],[2,3]]
                  So instead of having individual elements in a list, we have a list,
                  Then the set(list_tmp) will go wrong.

To study: The hash function