Instance variable inheritance problems

Question

For some unknown reason my program seems to be creating an instance of the character but not assigning an _id even though the _id even has a default in the __init__ .
I'm not sure why this is and yes I'm new to python and trying to learn OOP and inheritance to make sure I fully understood the tutorials I had watched I decided to create a kind of complex program for this.

class Entity(object):
    def __init__(self, _id = None):
        self._id = _id
        self._pos = (0, 0)
        self._vel = (0, 0)

# --------------------------------------------------------------

class Character(Entity):
    def __init__(self, _id = None, _name = None):
        self._id, self._name = _id, _name
        self._entity = Entity.__init__(self._id)

# --------------------------------------------------------------

character = Character(0, 'End')

The error's I get is as follow's...

File "test.py", line 119, in <module>
    character = Character(0, 'End')
File "test.py", line 59, in __init__
    self._entity = Entity.__init__(self._id)
File "test.py", line 5, in __init__
    self._id = _id

AttributeError: 'int' object has no attribute '_id'

I think this means that when a new object of Character/Entity is created it cannot find, init or define the _id variable? This is probably a simple error and I'm doing something very wrong but thanks in advance.

Answer 1

You are initializing the super-class incorrectly. You must pass self in as well:

self._entity = Entity.__init__(self, self._id)

However, it is easier to use super() in most cases:

self._entity = super().__init__(self._id)

In both cases:

character = Character(0, 'End')
print(vars(character))
# {'_id': 0, '_name': 'End', '_pos': (0, 0), '_vel': (0, 0), '_entity': None}

Also, it is pointless to assign the return value of the init (always None ) to self._entity . You can just make it

Entity.__init__(self, self._id)

or

super().__init__(self._id)