What is the name of the method to override the []
operator (subscript notation) for a class in Python?
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3 Answers
338
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__'
70
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
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Dave Kirby
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76`__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): ... – Don O'Donnell Dec 25 '09 at 18:15
17
You are looking for the __getitem__
method. See http://docs.python.org/reference/datamodel.html, section 3.4.6
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Confusion
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