Add a method to a list instance in python

Question

I want to add a method to a single instance of the 'list' class. Example:

a = [1,2]
a.first = lambda self: return self[0]

I know this don't work, but I want something like that works like that. I know its not a good practice, and I know I should do a whole new class, but I think this is possible in Python and haven't figured out how.

I am aware of: Dynamically add member function to an instance of a class in Python and Dynamically binding Python methods to an instance correctly binds the method names, but not the method

but none of those work with a native list.

Thanks!

You want to do `a.first = lambda: a[0]` or `a.first = types.MethodType(lambda self: self[0], a)`. If you add a function to an object like this Python won't automatically bind it to the object. — Peter Graham, Sep 22 '11 at 02:14
See http://stackoverflow.com/questions/6738987/extension-method-for-python-built-in-types — OlivierBlanvillain, Jan 07 '14 at 12:07

score 13 · Answer 1 · answered Sep 21 '11 at 22:18

13

Nothing will work with a native list, since you cannot add methods to a type defined in C. You will need to derive from list and add your method to that class.

answered Sep 21 '11 at 22:18

Ignacio Vazquez-Abrams

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Add a method to a list instance in python

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