Question

Which part of a dictionary element must be immutable?

Short answer

Answer: The key part of a dictionary element must be immutable because it is used as a unique identifier for the associated value and is involved in hashing to enable quick value lookups. If the key were mutable, its hash value could change, making it difficult to find the associated value in the dictionary.

Step-by-step solution

Understanding Dictionary Elements

A dictionary element consists of a key and a value. It is represented as key: value, where the key is used to locate its corresponding value in the dictionary.

Identifying the Immutable Part

In the context of a dictionary, the key must be an immutable (unchangeable) type like a string, integer, or tuple (if containing only immutable elements). This is because keys are used as unique identifiers for values and need to remain constant for a specific value to be accessible.

Reason for Immutability

The reasoning behind the immutability of keys is based on their use in the hashing process. The hash function allows the dictionary to quickly locate the value associated with a specific key. If the key were mutable, then its hash value could change, making it difficult to find the associated value in the dictionary.