This function takes a Python object and optional parameters for slicing and returns the start, stop, step ...

Jul 19, 2015 · First of all, I'd like to clarify the question: it's about the slice() function, not slices of lists or strings like a[5:4:3]. The docs mention that this function is used in NumPy and give no examples of usage (it's said how to use it but it's not said when to use it). Moreover, I've never seen this function used in any Python program.

Oct 12, 2010 · The slice function returns slice objects. Slice objects are one of Python's internal types, which are optimized for read performance - all of their attributes are read-only. Altering slice could be useful if wish to change the default behaviour.

We can then open up slice objects as: s = slice(1, 2, 3) assert s.start == 1 assert s.stop == 2 assert s.step == 3 This is notably used in Numpy to slice multi-dimensional arrays in any direction. Of course, any sane API should use ::3 with the usual "every 3" semantic. The related Ellipsis is covered further at: What does the Ellipsis object do?

Ellipsis is used mainly by the numeric python extension, which adds a multidimensional array type. Since there are more than one dimensions, slicing becomes more complex than just a start and stop index; it is useful to be able to slice in multiple dimensions as well. eg, given a 4x4 array, the top left area would be defined by the slice "[:2,:2]"

To extend Aaron's answer, for things like numpy, you can do multi-dimensional slicing by checking to see if given is a tuple:

Dec 4, 2012 · class SliceMaker(object): def __getitem__(self, item): return item make_slice = SliceMaker() print make_slice[3] print make_slice[0:] print make_slice[:-1] print make_slice[1:10:2,...] The idea is that you use make_slice[] instead of manually creating instances of slice. By doing this you'll be able to use the familiar square brackets syntax in ...

Feb 16, 2018 · You may use Python's slice() function with all the capabilities provided by the slice notation.Internally, both slice() function and the slice notation uses the slice object.

May 13, 2012 · I ran across this recently, while looking up how to have the user mimic the usual slice syntax of a:b:c, ::c, etc. via arguments passed on the command line. The argument is read as a string, and I'd rather not split on ':', pass that to slice(), etc. Besides, if the user passes a single integer i, the intended meaning is clearly a[i].

Slice is a JavaScript implementation of Python's awesome negative indexing and extended slice syntax for arrays and strings. It uses ES6 proxies to allow for an intuitive double-bracket indexing syntax which closely replicates how slices are constructed in Python.