Python-interface module Last Updated : 26 Mar, 2020 Summarize Suggest changes Share Like Article Like Report In object-oriented languages like Python, the interface is a collection of method signatures that should be provided by the implementing class. Implementing an interface is a way of writing an organized code and achieve abstraction. The package zope.interface provides an implementation of "object interfaces" for Python. It is maintained by the Zope Toolkit project. The package exports two objects, 'Interface' and 'Attribute' directly. It also exports several helper methods. It aims to provide stricter semantics and better error messages than Python's built-in abc module. Declaring interface In python, interface is defined using python class statements and is a subclass of interface.Interface which is the parent interface for all interfaces. Syntax : class IMyInterface(zope.interface.Interface): # methods and attributes Example Python3 1== import zope.interface class MyInterface(zope.interface.Interface): x = zope.interface.Attribute("foo") def method1(self, x): pass def method2(self): pass print(type(MyInterface)) print(MyInterface.__module__) print(MyInterface.__name__) # get attribute x = MyInterface['x'] print(x) print(type(x)) Output : <class zope.interface.interface.InterfaceClass> __main__ MyInterface <zope.interface.interface.Attribute object at 0x00000270A8C74358> <class 'zope.interface.interface.Attribute'> Implementing interface Interface acts as a blueprint for designing classes, so interfaces are implemented using implementer decorator on class. If a class implements an interface, then the instances of the class provide the interface. Objects can provide interfaces directly, in addition to what their classes implement. Syntax : @zope.interface.implementer(*interfaces) class Class_name: # methods Example Python3 import zope.interface class MyInterface(zope.interface.Interface): x = zope.interface.Attribute("foo") def method1(self, x): pass def method2(self): pass @zope.interface.implementer(MyInterface) class MyClass: def method1(self, x): return x**2 def method2(self): return "foo" We declared that MyClass implements MyInterface. This means that instances of MyClass provide MyInterface. Methods implementedBy(class) - returns a boolean value, True if class implements the interface else False providedBy(object) - returns a boolean value, True if object provides the interface else False providedBy(class) - returns False as class does not provide interface but implements it list(zope.interface.implementedBy(class)) - returns the list of interfaces implemented by a class list(zope.interface.providedBy(object)) - returns the list of interfaces provided by an object. list(zope.interface.providedBy(class)) - returns empty list as class does not provide interface but implements it. Python3 1== import zope.interface class MyInterface(zope.interface.Interface): x = zope.interface.Attribute('foo') def method1(self, x, y, z): pass def method2(self): pass @zope.interface.implementer(MyInterface) class MyClass: def method1(self, x): return x**2 def method2(self): return "foo" obj = MyClass() # ask an interface whether it # is implemented by a class: print(MyInterface.implementedBy(MyClass)) # MyClass does not provide # MyInterface but implements it: print(MyInterface.providedBy(MyClass)) # ask whether an interface # is provided by an object: print(MyInterface.providedBy(obj)) # ask what interfaces are # implemented by a class: print(list(zope.interface.implementedBy(MyClass))) # ask what interfaces are # provided by an object: print(list(zope.interface.providedBy(obj))) # class does not provide interface print(list(zope.interface.providedBy(MyClass))) Output : True False True [<InterfaceClass __main__.MyInterface>] [<InterfaceClass __main__.MyInterface>] [] Interface Inheritance Interfaces can extend other interfaces by listing the other interfaces as base interfaces. Functions extends(interface) - returns boolean value, whether one interface extends another. isOrExtends(interface) - returns boolean value, whether interfaces are same or one extends another. isEqualOrExtendedBy(interface) - returns boolean value, whether interfaces are same or one is extended by another. Python3 1== import zope.interface class BaseI(zope.interface.Interface): def m1(self, x): pass def m2(self): pass class DerivedI(BaseI): def m3(self, x, y): pass @zope.interface.implementer(DerivedI) class cls: def m1(self, z): return z**3 def m2(self): return 'foo' def m3(self, x, y): return x ^ y # Get base interfaces print(DerivedI.__bases__) # Ask whether baseI extends # DerivedI print(BaseI.extends(DerivedI)) # Ask whether baseI is equal to # or is extended by DerivedI print(BaseI.isEqualOrExtendedBy(DerivedI)) # Ask whether baseI is equal to # or extends DerivedI print(BaseI.isOrExtends(DerivedI)) # Ask whether DerivedI is equal # to or extends BaseI print(DerivedI.isOrExtends(DerivedI)) Output : (<InterfaceClass __main__.BaseI>, ) False True False True Advertise with us Next Article Difference between abstract class and interface in Python N naina024 Follow Similar Reads Python OOPs Concepts Object Oriented Programming is a fundamental concept in Python, empowering developers to build modular, maintainable, and scalable applications. 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