CODEWITHSUNDEEP
pythonpython-2.7inheritancesupernew-style-class
cjm2671
cjm2671

Reputation: 19476

Python 2.x super __init__ inheritance doesn't work when parent doesn't inherit from object

I have the following Python 2.7 code:

class Frame:
    def __init__(self, image):
        self.image = image

class Eye(Frame):
    def __init__(self, image):
        super(Eye, self).__init__()
        self.some_other_defined_stuff()

I'm trying to extend the __init__() method so that when I instantiate an 'Eye' it does a bunch of other stuff (self.some_other_defined_stuff()), in addition to what Frame sets up. Frame.__init__() needs to run first.

I get the following error:

super(Eye, self).__init__()
TypeError: must be type, not classobj

Which I do not understand the logical cause of. Can someone explain please? I'm used to just typing 'super' in ruby.

Upvotes: 30

Views: 48276

Answers (4)

ashwin r
ashwin r

Reputation: 1

Please write :__metaclass__ = type at the top of the code then we can Access super class

__metaclass__ = type
class Vehicle:
                def start(self):
                                print("Starting engine")
                def stop(self):
                                print("Stopping engine")                            
class TwoWheeler(Vehicle):
                def say(self):
                    super(TwoWheeler,self).start()
                    print("I have two wheels")
                    super(TwoWheeler,self).stop()                            
Pulsar=TwoWheeler()
Pulsar.say()

Upvotes: 0

Arjun Sharma
Arjun Sharma

Reputation: 1

Hi see my working codes for python 2.7

__metaclass__ = type
class Person:
    def __init__(self, first, last, age):
        self.firstname = first
        self.lastname = last
        self.age = age

    def __str__(self):
        return self.firstname + " " + self.lastname + ", " + str(self.age)

class Employee(Person):
    def __init__(self, first, last, age, staffnum):
        super(Employee, self).__init__(first, last, age)
        self.staffnumber = staffnum

    def __str__(self):
        return super(Employee, self).__str__() + ", " +  self.staffnumber


x = Person("Marge", "Simpson", 36)
y = Employee("Homer", "Simpson", 28, "1007")

print(x)
print(y)

Upvotes: -1

Mahdi Yusuf
Mahdi Yusuf

Reputation: 21038

Frame must extend object because only the new style classes support super call you make in Eye like so:

class Frame(object):
    def __init__(self, image):
        self.image = image

class Eye(Frame):
    def __init__(self, image):
        super(Eye, self).__init__(image)
        self.some_other_defined_stuff()

Upvotes: 13

Martijn Pieters
Martijn Pieters

Reputation: 1122512

There are two errors here:

  1. super() only works for new-style classes; use object as a base class for Frame to make it use new-style semantics.

  2. You still need to call the overridden method with the right arguments; pass in image to the __init__ call.

So the correct code would be:

class Frame(object):
    def __init__(self, image):
        self.image = image

class Eye(Frame):
    def __init__(self, image):
        super(Eye, self).__init__(image)
        self.some_other_defined_stuff()

Upvotes: 54

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