Python error using subclasses

Question

can you please tell me what I'm doing wrong?

here is a simple code for a Python subclass to create a person, just adding the name, and I want another class that will tell me the movies that he has rented, i'm just at the begining now

class Person(object):
    def __init__(self,name):
        self.name = name

class Customer(Person):
    def __init__(self):
        self.movie = []
        super(Customer,self).__init__()

but I get this error when I try to use my code

Johnny = Customer("John")

Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    Johnny = Customer("John"
TypeError: __init__() takes exactly 1 argument (2 given)

I'm new at Python and I don't really know what is going on!

Python is not C++; there is no function overloading. Why are you defining Person.__init__ twice? — user2555451
– user2555451, Commented Nov 6, 2014 at 21:12
Looks like a code block formatting problem. There's a newline missing somewhere in self.name = nameclass Customer(Person):. — Kevin
– Kevin, Commented Nov 6, 2014 at 21:12

Kevin · Accepted Answer · 2014-11-06 21:15:34Z

2

Assuming your code actually looks like this:

class Person(object):
    def __init__(self,name):
        self.name = name
class Customer(Person):
    def __init__(self):
        self.movie = []
        super(Customer,self).__init__()

Johnny = Customer("John")

You should modify your Customer class initializer so it also takes a name parameter. Don't forget to pass it during super, too.

class Customer(Person):
    def __init__(self, name):
        self.movie = []
        super(Customer,self).__init__(name)

answered Nov 6, 2014 at 21:15

Kevin

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1 Comment

Carlos Valencia Over a year ago

thank you!! I can vote you up because I don't have points, I'm sorry

John Y · Accepted Answer · 2014-11-06 22:37:19Z

1

You have defined the constructor for Person (Person.__init__) to take a single (non-self) argument named name:

class Person(object):
    def __init__(self,name):
        self.name = nameclass

But when you call Person.__init__ from your derived class constructor Customer.__init__ you are not supplying a value for that parameter. Because Person requires name in its constructor, you need to supply a value for it when you invoke it.

class Customer(Person):
    def __init__(self,name):
        self.movie = []
        super(Customer,self).__init__(name)

edited Nov 6, 2014 at 22:37

John Y

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answered Nov 6, 2014 at 21:15

Myk Willis

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2 Comments

Carlos Valencia Over a year ago

Thank for your answer!!, but, correct me if I'm wrong, isn't it the whole idea of inheritance to re-use the super class parameters, not having to declare them again in the subclasses??

John Y Over a year ago

@randomguy04: The idea of inheritance, at least in Python, is that any attribute you define for a child class completely replaces the same-named attribute in the parent class (if it exists). There is nothing which forces the child's __init__() to even call the parent's __init__() at all! That's why you have to do it explicitly if you want that behavior. And that's why Python can't assume that the parameters are going to be the same.

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