Overview

typed-proxy is a Python package that provides a metaclass for creating proxy classes with type annotations.

Install

To install typed-proxy, simply use pip:

$ pip install typed-proxy

Examples

Basic Usage

You can simply create a proxy class using the Proxy metaclass. The following example shows how to define a class Bar that proxies the class Foo.

from proxy import Proxy


class Foo:
    def __init__(self, a: int, b: int) -> None:
        self.a = a
        self.b = b

    def f1(self) -> None:
        print(f"Foo(a={self.a}, b={self.b}).f1()")

    def f2(self) -> None:
        print(f"Foo(a={self.a}, b={self.b}).f2()")

    def f3(self) -> None:
        print(f"Foo(a={self.a}, b={self.b}).f3()")


class Bar(Foo, metaclass=Proxy):
    def f2(self) -> None:
        print(f"Bar(a={self.a}, b={self.b}).f2()")


bar = Bar.proxy(Foo(1, 2))
bar.f1() # Foo(a=1, b=2).f1()
bar.f2() # Bar(a=1, b=2).f2()
bar.f3() # Foo(a=1, b=2).f3()

Accessing the Proxied Object

You can access the proxied object via the __proxied__ attribute in the proxy class.

class Bar(Foo, metaclass=Proxy):
    def f2(self) -> None:
        print(f"Bar(a={self.a}, b={self.b}).f2()")
        self.__proxied__.f2()


bar = Bar.proxy(Foo(1, 2))
bar.f1()  # Foo(a=1, b=2).f1()
bar.f2()  # Bar(a=1, b=2).f2() / Foo(a=1, b=2).f2()
bar.f3()  # Foo(a=1, b=2).f3()

Explicitly Defining __proxied__

Since type checkers cannot statically resolve __proxied__, they might raise an issue such as error: "Bar" has no attribute "__proxied__". To resolve this, you can explicitly define the __proxied__ attribute as follows.

class Bar(Foo, metaclass=Proxy):
    __proxied__: Foo

    def f2(self) -> None:
        print(f"Bar(a={self.a}, b={self.b}).f2()")
        self.__proxied__.f2()


bar = Bar.proxy(Foo(1, 2))
bar.f1()  # Foo(a=1, b=2).f1()
bar.f2()  # Bar(a=1, b=2).f2() / Foo(a=1, b=2).f2()
bar.f3()  # Foo(a=1, b=2).f3()

Custom __init__() for Proxy Class

You can define a custom __init__() method in the proxy class and provide arguments using the proxy() method with *args and **kwargs.

class Bar(Foo, metaclass=Proxy):
    def __init__(self, a: int, b: int, c: int):
        self.b = a
        self.c = b
        self.d = c

    def f3(self) -> None:
        print(f"Bar(a={self.a}, b={self.b}, c={self.c}, d={self.d}).f3()")


bar = Bar.proxy(Foo(1, 2), 3, 4, 5)
bar.f1()  # Foo(a=1, b=2).f1()
bar.f2()  # Foo(a=1, b=2).f2()
bar.f3()  # Bar(a=1, b=3, c=4, d=5).f3()