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+--- Thread: Native support for array-slicing syntax? (/thread-17731.html)
Native support for array-slicing syntax? - nxs - Apr-22-2019
Hello,
A newbie question on the 'how' of the array slicing syntax.
Given that,
- Python does not support NumPy style arrays natively;
- NumPy is a package that you must import;
- Imported packages cannot in general extend or modify the syntax of a language;
For example,
Quote:>>> from numpy import *
>>> a = array([ [1, 2, 3], [4, 5, 6], [7, 8, 9] ])
>>> a[:, 1:3]
array([[2, 3],
[5, 6],
[8, 9]])
>>>
In other words, if I were to create a NumPy-like package from scratch, what feature of Python would I use to support the colon-based syntax for slicing?
Many thanks.
Regards,
/nxs
RE: Native support for array-slicing syntax? - ichabod801 - Apr-22-2019
I don't know exactly how Numpy does it. But you could do it for your own classes by overriding __getitem__(key) and __setitem__(key, value). Whatever is in the brackets gets passed to those methods as the key parameter. In the example you give, it's a tuple of two slices. But as far as I know, it could be anything. And you could do anything with it. You could have it be the string 'one to five' and write code that would interpret that as 1:5 and return the appropriate slice of whatever.