Can you show an example of an object that cannot be hashed?

In Python, an object is not hashable if it is mutable and does not implement the __hash__ method. For example, lists (list) and dictionaries (dict) are not hashable because they are mutable.

Example:

my_list = [1, 2, 3]
try:
    hash(my_list)
except TypeError as e:
    print(f"Error: {e}")  # Will print: unhashable type: 'list'

Therefore, objects of type list, dict, set cannot be used as keys in dictionaries or as elements of sets because they are not hashable.