Is __iadd__ method supposed to change the data type of NumString?

I had the same question on this and I believe that is what's happening. The code given in the video is:

class NumString:
    def __init__(self, value):
        self.value = str(value)

    def __str__(self):
        return self.value

    def __int__(self):
        return int(self.value)

    def __float__(self):
        return float(self.value)

    def __add__(self, other):
        if '.' in self.value:
            return float(self) + other
        else:
            return int(self) + other

    def __radd__(self, other):
        return self + other

    def __iadd__(self, other):
        self.value = self + other
        return self.value

Then the example usage is:

>>> age = NumString(25)
>>> age += 1
>>> age
26

If age was still a NumString object, typing only ">>> age" into the console should have output something like "<numstring.NumString object at 0x7f4e251826d8>"

Looking at the Python documentation on iadd, using age += 1 is equivalent to age = age.iadd(1), so the return value of iadd is being assigned back to age, in this case the integer 26.

I tried a different implementation by returning self, rather than self.value. Additionally, I also converted the result of the add operation to a str, since the NumString object is expecting a string for its value attribute.

def __iadd__(self, other):
    self.value = str(self + other)
    return self

This seems to do what's expected:

>>> age = NumString(25)
>>> age += 1
>>> age
<numstring.NumString object at 0x7f5fe6cdb668>
>>> print(age)
26

Great point, Jon. I face the same problem. Yes, Jon's solution works for iadd. However, it doesn't work for imul. How come?