Added Type[C] implementation to typing.py.
diff --git a/Lib/typing.py b/Lib/typing.py
index 841e778..4bd2135 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -19,9 +19,10 @@
'Callable',
'Generic',
'Optional',
+ 'Tuple',
+ 'Type',
'TypeVar',
'Union',
- 'Tuple',
# ABCs (from collections.abc).
'AbstractSet', # collections.abc.Set.
@@ -447,6 +448,7 @@
# Some unconstrained type variables. These are used by the container types.
+# (These are not for export.)
T = TypeVar('T') # Any type.
KT = TypeVar('KT') # Key type.
VT = TypeVar('VT') # Value type.
@@ -456,6 +458,7 @@
T_contra = TypeVar('T_contra', contravariant=True) # Ditto contravariant.
# A useful type variable with constraints. This represents string types.
+# (This one *is* for export!)
AnyStr = TypeVar('AnyStr', bytes, str)
@@ -1572,6 +1575,35 @@
return super().__new__(cls, *args, **kwds)
+# Internal type variable used for Type[].
+CT = TypeVar('CT', covariant=True, bound=type)
+
+
+class Type(type, Generic[CT], extra=type):
+ """A generic type usable to annotate class objects.
+
+ For example, suppose we have the following classes::
+
+ class User: ... # Abstract base for User classes
+ class BasicUser(User): ...
+ class ProUser(User): ...
+ class TeamUser(User): ...
+
+ And a function that takes a class argument that's a subclass of
+ User and returns an instance of the corresponding class::
+
+ U = TypeVar('U', bound=User)
+ def new_user(user_class: Type[U]) -> U:
+ user = user_class()
+ # (Here we could write the user object to a database)
+ return user
+
+ joe = new_user(BasicUser)
+
+ At this point the type checker knows that joe has type BasicUser.
+ """
+
+
def NamedTuple(typename, fields):
"""Typed version of namedtuple.