Differences between Class Attribute and Instance Attribute of Python

example3.py

class MyClass(object):
    class_attr = 0

    def __init__(self, instance_attr):
        self.instance_attr = instance_attr
print(MyClass.__dict__)
# {'__module__': '__main__', 'class_attr': 0, '__init__': <function MyClass.__init__ at 0x7f00cb7fcea0>, '__dict__': <attribute '__dict__' of 'MyClass' objects>, '__weakref__': <attribute '__weakref__' of 'MyClass' objects>, '__doc__': None}
my_instance = MyClass(1)
print(my_instance.__dict__)
# {'instance_attr': 1}