naive slicing with Python objects

Asked Jul 10 '20 at 09:15

Active Jul 10 '20 at 09:23

Viewed 30 times

I have a Python class with __getitem__ that can receive a single integer and return some value,

class Coeffs:
    def __getitem__(self, k):
        # some computation
        return 2 * k ** 3 / 5


c = Coeffs()
print(c[4])

25.6

I would now like to have this class support slices à la c[1:4] by just calling the integer-version __getitem__ on all values in the slice.

Is there any simple or canonical way to do this?

edited Jul 10 '20 at 09:23

asked Jul 10 '20 at 09:15

Nico Schlömer

Print k and pass a slice in. Should tell you what you want. – Griffin Jul 10 '20 at 09:18
1

"I have a Python class with `__getitem__` that can receive a single integer and return some tuple" - I don't see a tuple here. – user2357112 Jul 10 '20 at 09:19
2

What you want is to [implement slicing in `__getitem__`](https://stackoverflow.com/questions/2936863/implementing-slicing-in-getitem). – paime Jul 10 '20 at 09:20
@Griffin Thanks for the comment. Is there a simple way to implement this? I don't want to reinvent the wheel. – Nico Schlömer Jul 10 '20 at 09:28
Is the link proposed by @paime not enough? – Serge Ballesta Jul 10 '20 at 09:29
`slice` has start, stop and step just like `range`. That should be all you need unless you get into using `Ellipsis` and/or tuples – Griffin Jul 10 '20 at 09:34

0 Answers0