Python 3: Comparing built-in objects to custom objects [duplicate]

When comparing ints and floats, Python 3 seems to take a bit of liberty:

>>> 1 == 1.0
True
>>> 1.0 == 1
True

I work on implementation of dozenal (base-12) numbers, and have overridden the __eq__ method to emulate the same behavior, and it almost works:

>>> a = Dozenal(1)
>>> a
DozenalInt('1')
>>> a == 1
debug_print: DozenalInt('1').__eq__(1) called
True
>>> 1 == a
debug_print: DozenalInt('1').__eq__(1) called
True
>>> a == 1.0
debug_print: DozenalInt('1').__eq__(1.0) called
True
>>> 1.0 == a
False

Why does it not try to call the reverse equality test in the last case, as it clearly does in others?

PS

__eq__ code really isn’t much to look at:

def __eq__(self, other):
    print('debug_print: {}.__eq__({}) called'.format(self.__repr__(), other.__repr__()))
    other = Dozenal._verify_other(other)
    if self.is_integer() and other.is_integer():
        return int(self) == int(other)
    return self._doz_cipher == other._doz_cipher

def _verify_other(other):
    if isinstance(other, Dozenal):
        return other
    elif isinstance(other, (int, float, str)):
        return Dozenal(other)
    else:
        return NotImplemented