Is it possible to use a list as a key in a dictionary?

In most programming languages, lists (or arrays) are mutable objects and cannot be used as keys in dictionaries (hash tables) because keys must be immutable and hashable.

For example, in Python, a list (list) cannot be used as a dictionary key because it is mutable and does not have a hash function:

my_dict = {}
my_list = [1, 2, 3]
my_dict[my_list] = 'value'  # will raise a TypeError

If you need to use a sequence as a key, you can use a tuple (tuple), which is immutable and hashable:

my_dict = {}
my_tuple = (1, 2, 3)
my_dict[my_tuple] = 'value'  # works correctly

Thus, a list as a key is not allowed, but immutable data structures are.