interface_vs_union_type.py

import typing as tp                                                                                                                                                                                                 
                                                                                                                                                                                                                    
class Abstract:                                                                                                                                                                                                     
    def func1(self, *, x: int, y: str):                                                                                                                                                                             
        raise NotImplementedError()                                                                                                                                                                                 
                                                                                                                                                                                                                    
class Foo(Abstract):                                                                                                                                                                                                
    @classmethod                                                                                                                                                                                                    
    def func1(cls, *, x, y):                                                                                                                                                                                        
        print(x)                                                                                                                                                                                                    
        print(y)                                                                                                                                                                                                    
                                                                                                                                                                                                                    
class Bar(Abstract):                                                                                                                                                                                                
    @classmethod                                                                                                                                                                                                    
    def func1(cls, *, x, y):  # pylint: disable=unused-argument                                                                                                                                                     
        print(x)                                                                                                                                                                                                    
                                                                                                                                                                                                                    
def bar1(x: tp.Type[Abstract]):                                                                                                                                                                                     
    x.func1(10, 20)                                                                                                                                                                                                 
                                                                                                                                                                                                                    
                                                                                                                                                                                                                    
# alternate implementation                                                                                                                                                                                          
                                                                                                                                                                                                                    
class Foo1(:                                                                                                                                                                                                        
    @classmethod                                                                                                                                                                                                    
    def func1(cls, *, x, y):                                                                                                                                                                                        
        print(x)                                                                                                                                                                                                    
        print(y)                                                                                                                                                                                                    
                                                                                                                                                                                                                    
class Bar1:                                                                                                                                                                                                         
    @classmethod                                                                                                                                                                                                    
    def func1(cls, *, x):                                                                                                                                         
        print(x)                                                                                                                                                                                                    
                                                                                                                                                                                                                    
Abstract1 = tp.Union[tp.Type[Foo1], tp.Type[Bar1]]                                                                                                                                                                  
                                                                                                                                                                                                                    
def bar2(x: Abstract1):                                                                                                                                                                                             
    if x is Foo:                                                                                                                                                                                                    
        x.func1(10, 20)                                                                                                                                                                                             
    elif x is Bar:                                                                                                                                                                                                  
        x.func1(10)                                                                                                                                                                                                 
    else:                                                                                                                                                                                                           
        raise ValueError(x)