In this post, we will be talking about how Python likes to deal with “list-like objects”. We will be diving into some quirks of Python that might seem a bit weird and, in the end, we will hopefully teach you how to build something that could actually be useful while avoiding common mistakes.

Part 1: Fake lists

Let’s start with this snippet.

class FakeList:
    def __getitem__(self, index):
        if index == 0:
            return "zero"
        elif index == 1:
            return "one"
        elif index == 2:
            return "two"
        elif index == 3:
            return "three"
        elif index == 4:
            return "four"
        elif index == 5:
            return "five"
        elif index == 6:
            return "six"
        else:
            raise IndexError(index)

f = FakeList()

A lot of people will be familiar with this:

f[3]
## <<< 'three'

__getitem__is the method you override if you want your instances to respond to the square bracket notation. Essentiallyf[3]is equivalent tof.__getitem__(3).

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