Python: Multiple Inheritance
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Multiple inheritance allows a subclass to inherit from multiple parent classes, combining their functionality. While simple in concept, it can be tricky to implement clearly. The simplest form is a mixin, where a class is designed to be inherited from to share methods and attributes without becoming a unique entity itself. The example demonstrates a MailSender mixin class that a EmailableContact class inherits from along with a Contact class, allowing send_mail functionality to be reused across classes.
Python: Multiple Inheritance
- 2. Multiple Inheritance • A subclass can inherit from multiple superclasses, and have the functionality of all of those superclasses available to it. • This is called Multiple Inheritance. • It sounds simple, and it is simple, but it is considered a very tricky to implement in a clear way.
- 3. Multiple Inheritance • The simplest and most useful form of multiple inheritance is called a mixin. • A MIXIN is a class that is specifically created to be a superclass that other classes will inherit methods and attributes from. • Let’s look at an example:
- 4. Multiple Inheritance • Let’s say we want to add functionality to our Contact class, to allow us to send an e-mail to self.email. • Sending an e-mail is a sufficiently general task that many other classes might use it also. • Let’s look at the MIXIN class for e-mailing:
- 5. Multiple Inheritance class MailSender: def send_mail(self, message) print(“Sending mail to ” + self.email) # e-mail logic here # END send_mail. # END class.
- 6. Multiple Inheritance • So now we can create a new class that uses both Contact and our new class MailSender class EmailableContact(Contact,MailSender): # Do stuff # END class.
- 7. Multiple Inheritance • So defining a class that uses multiple inheritance works a lot like calling a method with a number of parameters. We can test the new program with the following: >>>e = EmailableContact(“John Smith”, “[email protected]”) >>> e.send_mail(“Hello, test email”) Sending mail to [email protected]
- 8. etc.