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Python Object-Oriented Python Advanced Objects Multiplication

Posted by Kurobe Kuro^T_T^
Kurobe Kuro^T_T^
5,369 Points

Challenge Task 2 of 2 Now wrap it up by adding in __imul__, which does in-place multiplication. Be sure to update self.

i really dot get it

numstring.py 
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
        return int(self) + other

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

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

    def __mul__(self, other):
        if "." in self.value:
            return float(self) * other
        return int(self) * other


    def __rmul__(self, other):
        return self * other

    def __imul__(self, other): 
        self.value = self.value * other   
        return self.value

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,441 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,441 Points

You are close to having the correct answer. The goal of __imul__ is to retain the object type of self.value as a str.

Let's break down what you've tried:

    def __imul__(self, other): 
        self.value = self.value * other   
        return self.value

Since self.value is a string, multiplying it by a integer will result in a repeated string, not a new string containing the updated number. With the __mul__ method is available, use it to do the multiplication. To trigger the use of __mul__, use self as the multiplicand in place of self.value. This gives us:

        self.value = self * other

One drawback is __mul__ returns an integer instead of string. To fix this, wrap the multiplication with str():

        self.value = str(self * other)

Post back if you need more help. Good luck!!

Kurobe Kuro^T_T^
Kurobe Kuro^T_T^
5,369 Points

thank you id figure it out :D