Disclaimer: I am not asking if the upper-bound stopargument of slice()and range() is exclusive or how to use these functions.

Calls to the rangeand slicefunctions, as well as the slice notation [start:stop] all refer to sets of integers.

range([start], stop[, step])
slice([start], stop[, step])

In all these, the stop integer is excluded.

I am wondering why the language is designed this way.

Is it to make stopequal to the number of elements in the represented integer set when start equals 0 or is omitted?

Is it to have:

for i in range(start, stop):

look like the following C code?

for (i = start ; i < stop; i++) {

I know that when I use range([start], stop[, step]) or slice([start], stop[, step]), the stop value is not included in the range or slice.

But why does it work this way?

Is it so that e.g. a range(0, x) or range(x) will contain x many elements?

Is it for parallelism with the C for loop idiom, i.e. so that for i in range(start, stop): superficially resembles for (i = start ; i < stop; i++) {?

_{See also Loop backwards using indices for a case study: setting the stop and step values properly can be a bit tricky when trying to get values in descending order.}