adding new methods to established classes

Question

I would like to extend the list functionality, so we can used as below. How can add this methods to the list object?

  # list([1,2,3,4,5]).even() should return [2,4]

You can't (well, without rewriting Python's source code). You're better off subclassing `list`. — , Dec 15 '14 at 23:18
You could do somersaults, maybe the good point is to point to the following . — nbro, Dec 15 '14 at 23:21
You can [add](http://stackoverflow.com/questions/972/adding-a-method-to-an-existing-object) methods to objects though. — Marcin, Dec 15 '14 at 23:22
@Marcin But not to lists, because they are implemented in C. — Daniel Roseman, Dec 15 '14 at 23:24
You can either subclass `list` or create a utility function that takes the list and manipulate it the way you want. — Addison, Dec 16 '14 at 01:27

score 1 · Accepted Answer · answered Dec 15 '14 at 23:24

You can't monkey patch list because it is defined in C extension modules and is therefore inmutable in this sense. You can subclass list:

class mylist(list):
    def even(self):
        return [x for x in self if x % 2 == 0]

>>> mylist([1,2,3,4,5]).even()
[2, 4]

1 Answers1