A protocol P1 is assignable to another protocol P2 if P1 defines all protocol members of P2 with assignable types. Generic protocol types follow the same rules of variance as non-protocol types. Protocol types can be used in all contexts where any other types can be used, such as in unions, ...

July 25, 2024 - Protocol classes can be generic. To create a generic protocol, you can use the typing.TypeVar class.

March 5, 2017 - Generic protocol types follow the same rules of variance as non-protocol types. Protocol types can be used in all contexts where any other types can be used, such as in Union, ClassVar, type variables bounds, etc.

Protocols can also be generic (see also Protocols and structural subtyping). Several predefined protocols are generic, such as Iterable[T], and you can define additional generic protocols. Generic protocols mostly follow the normal rules for generic classes.

Mypy supports generic protocols (see also Protocols and structural subtyping). Several predefined protocols are generic, such as Iterable[T], and you can define additional generic protocols. Generic protocols mostly follow the normal rules for generic classes. Example (Python 3.12 syntax):

December 7, 2024 - This functionality is beneficial for delivering common or generic implementations that can serve as a fallback or standard behavior. This aspect of Protocols resembles Scala or Rust's traits. Traits allow the bundling of method definitions with an interface. While the Protocol's primary benefit is develop-time-checked structural typing, adding default implementations brings a flavor of trait-like functionality to the language. It's important to note that classes in Python do not need to be directly inherited from a Protocol to be considered as implementing that Protocol.

December 28, 2023 - Protocol can be applied to all members within the class, encompassing variables, functions, and abstract methods. Another noteworthy topic is the “Generic Protocol.” Using the above code as an example, consider the scenario where we have input for the run function, and we want to make it compatible with both int and str.

In Python 3.9 and later, the aliases in typing don’t provide any extra functionality. You can define your own protocol class by inheriting the special Protocol class:

Mypy supports generic protocols (see also Protocols and structural subtyping). Several predefined protocols are generic, such as Iterable[T], and you can define additional generic protocols. Generic protocols mostly follow the normal rules for generic classes. Example (Python 3.12 syntax):

February 15, 2022 - from dataclasses import dataclass from typing import Generic, Protocol, TypeVar import pandas as pd _DataFrameBound = TypeVar("_DataFrameBound", bound=pd.DataFrame, covariant=True) class _Method(Protocol[_DataFrameBound]): def __call__(self, ...

May 17, 2024 - class Applicative(Functor[A], Protocol[A]): @staticmethod def pure(x: Any) -> Applicative[A]: ... @staticmethod def ap(f: Applicative[Callable[[A], B]], x: Applicative[A]) -> Applicative[B]: ... class Monad(Applicative[A], Protocol[A]): @staticmethod def bind(x: Monad[A], f: Callable[[A], Monad[B]]) -> Monad[B]: ... @dataclass class Io(Generic[A]): action: Callable[[], A] @staticmethod def fmap(f: Callable[[A], B], x: Io[A]) -> Io[B]: return Io(lambda: f(x.action())) @staticmethod def pure(x: A) -> Io[A]: return Io(lambda: x) @staticmethod def ap(f: Io[Callable[[A], B]], x: Io[A]) -> Io[B]: return Io(lambda: f.action()(x.action())) @staticmethod def bind(x: Io[A], f: Callable[[A], Io[B]]) -> Io[B]: return Io(lambda: f(x.action()).action()) def taking_monad(x: Monad[int]) -> bool: return True taking_monad(Io(lambda: 1))

November 21, 2024 - A protocol defines what methods and behaviors a class must have, but it doesn’t need to be explicitly inherited. As long as the object follows the “rules” (method signatures), it is treated as a valid implementation, even if it’s not a subclass. This is duck typing in action! My first impression of TypeVar and Generic in Python was: why are we using two things for one type?!

July 9, 2024 - import abc from typing import Generic, Protocol, TypedDict, TypeVar class BaseResult(TypedDict): """ Result """ R = TypeVar("R", bound=BaseResult) R_contra = TypeVar("R_contra", bound=BaseResult, contravariant=True) class BadProtocolResultWriter(Protocol[R]): """ Type variable "R" used in generic protocol "ProtocolResultWriter" should be contravariant (reportInvalidTypeVarUse) main.py:16: error: Invariant type variable "R" used in protocol where contravariant one is expected [misc] """ @abc.abstractmethod def write( self, result: R, ) -> None: """ Write to destination """ class ABCResultWriter(abc.ABC, Generic[R]): """ This type checks just fine, but what is different compared to the Protocol equivalent?

June 23, 2021 - In this article, we're going to ... typing, and other idiomatic patterns in Python. Protocol is a very generic word, both in regular language as well as in Computer Science....

1 month ago - Protocol classes decorated with runtime_checkable() (described later) act as simple-minded runtime protocols that check only the presence of given attributes, ignoring their type signatures. Protocol classes without this decorator cannot be used as the second argument to isinstance() or issubclass(). ... In code that needs to be compatible with Python 3.11 or older, generic Protocols can be written as follows:

July 25, 2022 - The protocol class implementation defines rules and guidelines for implementing protocol methods within a class, including the use of variable annotations. Python Protocol class variables are defined within the class body of a protocol, and there is a distinction between protocol class variables and protocol instance variables.

October 5, 2022 - Instead of having typing.Protocol, which we inherit to define a Protocol class, we could have a global @protocol decorator that declares a class as a Protocol. And the class that adheres to that Protocol should be decorated with a decorator having the name of the Protocol class it adheres to.

November 6, 2018 - from dataclasses import dataclass from typing import Union, ClassVar, TypeVar, Generic, Type from typing_extensions import Protocol _P = TypeVar('_P', bound='PType') class PType(Protocol): @classmethod def maximum_type_value(cls: Type[_P]) -> _P: ... @classmethod def minimum_type_value(cls: Type[_P]) -> _P: ...

May 8, 2019 - test.py:20:1: error: Invariant type variable 'T' used in protocol where contravariant one is expected test.py:24:5: error: Function is missing a return type annotation · What are the versions of mypy and Python you are using? Do you see the same issue after installing mypy from Git master?