Super

Date: February 5th 2016
Last updated: February 6th 2016

The super method returns an object of the parent class. Super is almost always used for multiple inheritance. It might not matter so much for inheritance from a single parent class.

Here are some useful resources:

• how to use super
• python 201: what is super (and links within)
• super considered super
• using super effectively
• structuring super calls

Inheriting attributes:

The following example was inspired by the content in python 3: object oriented programming by Dusty Phillips.

A useful part of the following code occurs when Clients() is instantiated. Both name and phone number are added to my_contacts list. This is because super calls the init method in Contacts which appends the contact information.

class ContactList(list):
    pass

# note that in python 2.7 Contacts must inherit from object
class Contacts(object):
    my_contacts = ContactList()

    def __init__(self, name):
        self.name = name
        self.my_contacts.append(self)


class Clients(Contacts):
    def __init__(self, name, phone):
        # add the new attribute for Clients
        self.phone = phone        

        # make sure super calls THIS class (Clients)and not the one
        # you are trying to inherit from! I kept trying to 
        # call super(Contacts, self) which 'obviously' failed 
        super(Clients, self).__init__(name)

        # another python 2.7 option
        # super(self.__class__, self).__init__(name)

        # python 3 is different...
        # super().__init__(name)


gf = Contacts('Jane') 
me = Clients('Mike', '0247324004') 
# dont instantiate...
Contacts('Richard') #returns: <__main__.Contacts object at 0x7f69742ef090>

[c.name for c in me.my_contacts]
#returns: ['Jane', 'Mike', 'Richard'] 

# note that Richard still made the contacts list (class method of Contacts)
# note that Mike is also in the contacts list (name is initialised from Contacts)

Inheriting methods:

The following example was inspired by content in Python in a nutshell by Alex Martelli.

class base(object):
    def mymethod(self):
        print "base method"

class satellite(base):
    def mymethod(self):
        print "satellite method"
        super(satellite, self).mymethod()

satellite().mymethod()
#returns:
#>>> satellite method
#>>> base method