In 3.10 the union type (the type of the result of the | operator for types) was added (https://www.python.org/dev/peps/pep-0604/). It is exposed as types.Union. There are differences between typing.Union and types.Union: * typing.Union is indexable, types.Union is not. * types.Union is a class, typing.Union is not. types.Union corresponds to private class typing._UnionGenericAlias, not typing.Union. It is confusing that typing.Union and types.Union have the same name but are so different. Note also that most classes in the types module have the "Type" suffix: FunctionType, MethodType, ModuleType, etc. I think that it would be better to rename types.Union to types.UnionType. The name of types.Union is the part of already accepted PEP 604, so we need to hear opinions of authors, sponsor and BDFL-delegate of the PEP. I did not participate in the discussion about PEP 604 so I do not know if there are arguments in favor of types.Union over types.UnionType.