What is a hashable data type?

In software engineering, a hashable data type is a data type that can be used as an input to a hash function. A hash function takes an input, known as a hashable object, and returns a fixed-size string of characters, called the hash value.

The hash value is typically used as a unique identifier for the original object and can be used for efficient data structure operations, such as searching and sorting. For a data type to be hashable, it must have a consistent hash value for a given object throughout the object's lifetime, and it must be immutable (cannot change after it has been created).

Examples of hashable data types in Python include integers, strings, and tuples containing only hashable elements.