The obvious solution to the problem is to use issubclass
, but this raises TypeError
(using Python 3.6.7), e.g.
>>> from typing_extensions import Protocol
>>> class ProtoSubclass(Protocol):
... pass
...
>>> issubclass(ProtoSubclass, Protocol)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/opt/conda/envs/airflow/lib/python3.6/site-packages/typing_extensions.py", line 1265, in __subclasscheck__
raise TypeError("Instance and class checks can only be used with"
TypeError: Instance and class checks can only be used with @runtime protocols
>>> from typing_extensions import runtime
>>> @runtime
... class ProtoSubclass(Protocol):
... pass
...
>>> issubclass(ProtoSubclass, Protocol)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/opt/conda/envs/airflow/lib/python3.6/site-packages/typing_extensions.py", line 1265, in __subclasscheck__
raise TypeError("Instance and class checks can only be used with"
TypeError: Instance and class checks can only be used with @runtime protocols
For more on the topic of python Protocols
, see
In Python 3.6.7, one way to solve this is to use the @runtime_checkable
decorator:
>>> from typing_extensions import Protocol
>>> from typing_extensions import runtime_checkable
>>> @runtime_checkable
... class CustomProtocol(Protocol):
... def custom(self):
... ...
...
>>> @runtime_checkable
... class ExtendedCustomProtocol(CustomProtocol, Protocol):
... def extended(self):
... ...
...
>>> issubclass(ExtendedCustomProtocol, CustomProtocol)
True