What is the name of the method to override the [] operator (subscript notation) for a class in Python?
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3 Answers
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__'
Comments
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
1 Comment
Don O'Donnell
__getslice__, __setslice__` and __delslice__' have been deprecated for the last few releases of ver 2.x (not sure exactly when), and are no longer supported in ver 3.x. Instead, use __getitem__. __setitem__` and __delitem__' and test if the argument is of type slice, i.e.: if isinstance(arg, slice): ...You are looking for the __getitem__ method. See http://docs.python.org/reference/datamodel.html, section 3.4.6
