Python set Add causes problem typeerror:unhashable type: ' List '

Problem recurrence

>>> A =set ()>>> B =set ()>>> B.add (1)>>>A.add (b) Traceback (most recent): File"<stdin>", Line 1,inch<module>typeerror:unhashable Type:'Set'
>>> C =list (b)>>>A.add (c) Traceback (most recent): File"<stdin>", Line 1,inch<module>typeerror:unhashable Type:'List'

>>>tuple (b) (1,)
>>> A.add (b)
>>>

Phenomenon: When you add a list or collection object to a set object, you are prompted that they are not hashed, but for a tuple type.

Cause: The object in set is a hash store (so it's unordered), for Python Everything is an object, if a list object is stored, then the list object is changed, then the hash of the value just stored in the set is changed.

Conclusion: Set is a hash store and must store immutable objects, such as strings, numbers, tuples, and so on.

Python set Add causes problem typeerror:unhashable type: ' List '