NoneType

NoneType is the type of the None object in Python. None represents the absence of a value or a null result, and it is implemented as a singleton within a running program. The type of None can be obtained at runtime with type(None), which yields NoneType; there is no separate constructor for creating additional instances of None.

None is immutable and hashable, and it is considered falsy in boolean contexts, so bool(None) evaluates to False. The recommended way to check for the absence of a value is to compare with None using the identity operator is (for example, if x is None:). Using equality (==) is discouraged in favor of is, because None is a unique singleton and its identity should be preserved.

A common role for None is to indicate a missing value or the end of a computation. Functions that do not explicitly return a value return None. It is also frequently used as a default argument value or as a placeholder in data structures. When data is serialized to JSON, None is converted to null, reflecting the absence of a value.

In type annotations, None is used in conjunction with Optional[T] to denote that a value can be either of type T or None. This helps express the possibility of missing or unspecified values in function signatures and data models.

None has no meaningful methods of its own; it is the value, not an object with behavior, and most operations on None rely on its identity, truthiness, and its role as a placeholder for "no value."