Hashing arrays in Python

Hashing arrays in Python

Just try it:

>>> hash((1,2,3))
2528502973977326415
>>> hash([1,2,3])
Traceback (most recent call last):
  File <stdin>, line 1, in <module>
TypeError: unhashable type: list
>>> hash(frozenset((1,2,3)))
-7699079583225461316
>>> hash(set((1,2,3)))
Traceback (most recent call last):
  File <stdin>, line 1, in <module>
TypeError: unhashable type: set

So you can get hash of tuple and frozenset since the are immutable, and you cant do it for list and set because they are mutable.

If you really need to use a list as a dictionary key, try converting it to a string first.
my_list = str(my_list)

Hashing arrays in Python

Python doesnt allow you to use mutable data as keys in dictionaries, because changes after insertion would make the object un-findable. You can use tuples as keys.