CODEWITHSUNDEEP
pythonoperator-overloading
Sahas
Sahas

Reputation: 11399

How to override the [] operator in Python?

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

Upvotes: 359

Views: 206338

Answers (3)

David Webb
David Webb

Reputation: 193686

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__'

Upvotes: 461

Confusion
Confusion

Reputation: 16841

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

Upvotes: 24

Dave Kirby
Dave Kirby

Reputation: 26552

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

Upvotes: 91

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