Overloading * and float() for a Fraction Class

How do `a * b`, `a.__mul__(b)` and `Fraction.__mul__(a, b)` all run the same code, and why is only the last handed `self` by hand?

Finger exercises

Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.

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Exercise 1 of 5

Teach `Fraction` what the star means

The Fraction class below can build itself and print itself, but a * b currently fails — nothing in the class says what a star between two fractions should mean.

Add __mul__, the method Python runs behind the * shorthand, so that multiplying two fractions multiplies the numerators, multiplies the denominators, and hands back a new Fraction object rather than a float. Then multiply a, which is 2/5, by b, which is 3/7, and assign the result to product.

class Fraction(object):
    """ A number of the form num/denom, where both are integers """

    def __init__(self, num, denom):
        """ Sets the numerator and the denominator """
        self.num = num
        self.denom = denom

    def __str__(self):
        """ Returns the fraction written as num/denom """
        return str(self.num) + "/" + str(self.denom)

    # your code here: add the __mul__ method


a = Fraction(2, 5)
b = Fraction(3, 7)

# The product of a and b.
product = ...  # your code here

class Fraction(object):
    """ A number of the form num/denom, where both are integers """

    def __init__(self, num, denom):
        """ Sets the numerator and the denominator """
        self.num = num
        self.denom = denom

    def __str__(self):
        """ Returns the fraction written as num/denom """
        return str(self.num) + "/" + str(self.denom)

    # your code here: add the __mul__ method


a = Fraction(2, 5)
b = Fraction(3, 7)

# The product of a and b.
product = ...  # your code here

Python runs in your browser

⌘/Ctrl + Enter runs

`Fraction` has a `__mul__` method

the product is a `Fraction`, not a float

multiplies numerators and denominators straight across

works for any pair of fractions, and reduces nothing

←Previous The __str__ Method: You Decide What print Shows Next Inside reduce: a Nested gcd and the Branch That Returns an int →

Overloading * and float() for a Fraction Class

How do `a * b`, `a.__mul__(b)` and `Fraction.__mul__(a, b)` all run the same code, and why is only the last handed `self` by hand?

Finger exercises

Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.

0 / 5 passed

Exercise 1 of 5

Teach `Fraction` what the star means

The Fraction class below can build itself and print itself, but a * b currently fails — nothing in the class says what a star between two fractions should mean.

class Fraction(object):
    """ A number of the form num/denom, where both are integers """

    def __init__(self, num, denom):
        """ Sets the numerator and the denominator """
        self.num = num
        self.denom = denom

    def __str__(self):
        """ Returns the fraction written as num/denom """
        return str(self.num) + "/" + str(self.denom)

    # your code here: add the __mul__ method


a = Fraction(2, 5)
b = Fraction(3, 7)

# The product of a and b.
product = ...  # your code here

class Fraction(object):
    """ A number of the form num/denom, where both are integers """

    def __init__(self, num, denom):
        """ Sets the numerator and the denominator """
        self.num = num
        self.denom = denom

    def __str__(self):
        """ Returns the fraction written as num/denom """
        return str(self.num) + "/" + str(self.denom)

    # your code here: add the __mul__ method


a = Fraction(2, 5)
b = Fraction(3, 7)

# The product of a and b.
product = ...  # your code here

Python runs in your browser

⌘/Ctrl + Enter runs

`Fraction` has a `__mul__` method

the product is a `Fraction`, not a float

multiplies numerators and denominators straight across

works for any pair of fractions, and reduces nothing

←Previous The __str__ Method: You Decide What print Shows Next Inside reduce: a Nested gcd and the Branch That Returns an int →

Overloading * and float() for a Fraction Class

Teach Fraction what the star means

Overloading * and float() for a Fraction Class

Teach Fraction what the star means

Teach `Fraction` what the star means

Teach `Fraction` what the star means