Python: TypeError: init() takes exactly 5 arguments (6 given)

Question

I've been having this issue with this code, and I'm not sure why I'm still getting this TypeError here. I have the following Animal class, which is the base class for the Dog class defined below it. I want to create a Dog object which inherits from this Animal class.

Here's the Animal class:

class Animal(object):
    __name = None
    __height = None
    __weight = None
    __sound = None

    def __init__(self, name, height, weight, sound):
        self.__name = name
        self.__height = height
        self.__weight = weight
        self.__sound = sound

    def set_name(self, name):
        self.__name = name

    def set_height(self, height):
        self.__height = height

    def set_weight(self, height):
        self.__height = height

    def set_sound(self, sound):
        self.__sound = sound

    def get_name(self):
        return self.__name

    def get_height(self):
        return str(self.__height)

    def get_weight(self):
        return str(self.__weight)

    def get_sound(self):
        return self.__sound

    def get_type(self):
        print("Animal")

    def toString(self):
        return "{} is {} cm tall and {} kilograms and says {}".format(self.__name, self.__height, self.__weight, self.__sound)

And then I have the following Dog class which inherits from the above Animal class:

class Dog(Animal):
    __owner = None

    def __init__(self, name, height, weight, sound, owner):
        self.__owner = owner
        super(Dog, self).__init__(self, name, height, weight, sound)

    def set_owner(self, owner):
        self.__owner = owner

    def get_owner(self):
        return self.__owner

    def get_type(self):
        print("Dog")

    def toString(self):
        return "{} is {} cm tall and {} kilograms and says {}. His owner is {}".format(self.__name, self.__height, self.__weight, self.__sound, self.__owner)

When I try to create a Dog object with the following code:

spot = Dog('Spot', 22, 11, 'Bark', 'John')

I get the following TypeError:

TypeError: __init__() takes exactly 5 arguments (6 given)

Does anyone know why I'm getting this error? I'm not really understanding what's going on here.

Thanks in advance!

Edit: After taking out the self from the superclass, I now am getting an AttributeError: 'Dog' object has no attribute '_Dog__name' when I try the following code:

print(spot.toString())

Just drop first self from superclass, it's implicitly passed via super call. — Łukasz Rogalski
– Łukasz Rogalski, Commented May 31, 2016 at 16:11
This isn't Java. You shouldn't be writing a dozen getters and setters, or using double-underscore names unnecessarily, or declaring instance attributes at class level, or calling your string conversion method toString. — user2357112
– user2357112, Commented May 31, 2016 at 16:12
Thanks for the heads up. This is actually code from an online tutorial, and I'll keep what you said in mind. — Asad
– Asad, Commented May 31, 2016 at 16:18
@AsadMehdi the whole point of using two underscores is so that sources outside the class cannot access them (Including your Dog subclass) you will need to use the self.get_name() instead of self.__name from your Dog class (otherwise what is the point of the getters anyway?) — Tadhg McDonald-Jensen
– Tadhg McDonald-Jensen, Commented May 31, 2016 at 16:30

Łukasz Rogalski · Accepted Answer · 2016-05-31 16:13:13Z

2

Problem lays in __init__ method of superclass. super() call implicitly passes self as first argument. Simply use:

def __init__(self, name, height, weight, sound, owner):
    self.__owner = owner
    super(Dog, self).__init__(name, height, weight, sound)

Explicit self is necessary only when you refer to superclass by it's name.

def __init__(self, name, height, weight, sound, owner):
    self.__owner = owner
    Animal.__init__(self, name, height, weight, sound)

answered May 31, 2016 at 16:13

Łukasz Rogalski

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3 Comments

Asad Over a year ago

Thanks for the quick reply. However, I'm now getting the following error: AttributeError: 'Dog' object has no attribute '_Dog__name' I actually tried to do what you suggested before, but reverted back when I started getting this error. Do you know what's wrong here? I should also mention that I am doing this after constructing the Dog object: print(spot.toString()). I'll add this in my original post.

Łukasz Rogalski Over a year ago

You have just experienced name mangling mechanism

Łukasz Rogalski Over a year ago

@AsadMehdi If answer was helpful, please accept it.

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