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A new approach to interfaces in Python

Project description

Python Strict Interfaces

Installation

pip install strict-interfaces

Design Goals

  • Be as strict as possible
  • Fail on import time
  • Do not mess with object and/or type inheritance
  • Possibility to integrate in CPython Core
  • Ability to use "out of the box" regardless support in an interpreter

Features

  • Special keyword implements on the class definition
  • Multiple interface implementation
  • Implicit interface implementation
  • Interface inheritance with overloading being restricted
  • Special isimplementation function similar to issubclass
  • Partial issubclass support (see below)
  • It's restricted to create an interface instance
  • It's restricted to inherit from object and interface at the same time

Usage

Explicit implementation

class TestInterface(interfaces.interface):
    def method(self, arg: typeT1) -> typeT2:
        pass

class TestClass(interfaces.object, implements=[TestInterface]):
    def method(self, arg: typeT1) -> typeT2:
        pass

Raises when is not implemented

class TestInterface(interfaces.interface):
    def method(self, arg):
        pass

class TestClass(interfaces.object, implements=[TestInterface]):
    pass

Implicit implementation and run-time check

class TestInterfaceA(interfaces.interface):
    def method_a(arg: typeT1) -> typeT1:
        pass

class TestInterfaceB(interfaces.interface):
    def method_b(arg: typeT2) -> typeT2:
        pass

class TestClass:
    def method_a(arg: typeT1) -> typeT1:
        pass

    def method_b(arg: typeT2) -> typeT2:
        pass

assert interfaces.isimplementation(TestClass, (TestInterfaceA, TestInterfaceB))

isimplementation checks whether all interfaces are implemented

class TestInterfaceA(interfaces.interface):
    def method_a(arg: typeT1) -> typeT1:
        pass

class TestInterfaceB(interfaces.interface):
    def method_b(arg: typeT2) -> typeT2:
        pass

class TestClass:
    def method_a(arg: typeT1) -> typeT1:
        pass

# NOTE: In this case `isimplementation` behaves different than `issubclass`
assert not interfaces.isimplementation(TestClass, (TestInterfaceA, TestInterfaceB))
assert issubclass(TestClass, (TestInterfaceA, TestInterfaceB))

Contributing

Pull requests, feature requests, and bug reports are always welcome!

github.com/lig/python-interfaces

Project details


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