Question

I am wondering if it is possible to write count(vanilla) instead of vanilla.count() ? It is similar to len(list) but I want to do len(myclass). Is it possible to implement like this on my user define class? Below just a dummy class I wrote to ask this question. Thank you.

    class IceCream():
    # Flavor is a string
    # Toppings is a list of strings
    def __init__(self, flavor, toppings, ):
        self.name = flavor
        self.toppings = toppings
    # Return the number of toppings
    def count(self):
        return len(self.toppings)
    def __str__(self):
        return "{0} flavor ice cream".format(self.name)


vanillaToppings = ['chocolate chips', 'fudge', 'penuts']
vanilla = IceCream('Vanilla', vanillaToppings)
print(vanilla, 'with', vanilla.count(), 'kind of toppings!')
# Is it possible? If so, how do I do it?
# print(vanilla, 'with', len(vanilla), 'kind of toppings!')

Answer 1

How about utilizing one of python’s special methods: __len__?

Called to implement the built-in function len(). Should return the length of the object, an integer >= 0.

class IceCream():
    # Flavor is a string
    # Toppings is a list of strings
    def __init__(self, flavor, toppings):
        self.name = flavor
        self.toppings = toppings

    # Return the number of toppings
    def __len__(self):
        return len(self.toppings)

    def __str__(self):
        return "{0} flavor ice cream".format(self.name)


vanillaToppings = ['chocolate chips', 'fudge', 'penuts']
vanilla = IceCream('Vanilla', vanillaToppings)
print(vanilla, 'with', len(vanilla), 'kind of toppings!')

I would guess that the meaning of count and length are somewhat interchangeable in this case, so why not use something familiar?