How to override the [] operator in Python?

Question

What is the name of the method to override the [] operator (subscript notation) for a class in Python?

Answer 1

You need to use the __getitem__ method.

class MyClass:
    def __getitem__(self, key):
        return key * 2

myobj = MyClass()
myobj[3] #Output: 6

And if you're going to be setting values you'll need to implement the __setitem__ method too, otherwise this will happen:

>>> myobj[5] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: MyClass instance has no attribute '__setitem__'

Answer 2

To fully overload it you also need to implement the __setitem__and __delitem__ methods.

edit

I almost forgot... if you want to completely emulate a list, you also need __getslice__, __setslice__ and __delslice__.

There are all documented in http://docs.python.org/reference/datamodel.html

Answer 3

You are looking for the __getitem__ method. See http://docs.python.org/reference/datamodel.html, section 3.4.6