Only very rarely does Python add a new standard data type. Python 3.15, when it’s released later this year, will come with one—an immutable dictionary, frozendict.
Dictionaries in Python correspond to hashmaps in Java. They are a way to associate keys with values. The Python dict, as it’s called, is tremendously powerful and versatile. In fact, the dict structure is used by the CPython interpreter to handle many things internally.
But a dict has a big limitation: it’s not hashable. A hashable type in Python has a hash value that never changes during its lifetime. Strings, numerical values (integers and floats), and tuples are all hashable because they are immutable. Container types, like lists, sets, and, yes, dicts, are mutable, so can’t guarantee they hold the same values over time.
