Python class inheritance: AttributeError: '[SubClass]' object has no attribute 'xxx'

Question

I have the following base class and subclass:

class Event(object):
    def __init__(self, sr1=None, foobar=None):
        self.sr1 = sr1
        self.foobar          


        

Answer 1

You're overriding the constructor (__init__) of the parent class. To extend it, you need to explicitly call the constructor of the parent with a super() call.

class TypeTwoEvent(Event):
    def __init__(self, level=None, **kwargs):
        # the super call to set the attributes in the parent class
        super(TypeTwoEvent, self).__init__(**kwargs)
        # now, extend other attributes
        self.sr1 = level
        self.state = STATE_EVENT_TWO

Note that the super call is not always at the top of the __init__ method in your sub-class. Its location depends on your situation and logic.