Why does range(start, end) not include end?

CloudMeta picture CloudMeta · Dec 21, 2010 · Viewed 319.5k times · Source
>>> range(1,11)

gives you

[1,2,3,4,5,6,7,8,9,10]

Why not 1-11?

Did they just decide to do it like that at random or does it have some value I am not seeing?

Answer

moinudin picture moinudin · Dec 21, 2010

Because it's more common to call range(0, 10) which returns [0,1,2,3,4,5,6,7,8,9] which contains 10 elements which equals len(range(0, 10)). Remember that programmers prefer 0-based indexing.

Also, consider the following common code snippet:

for i in range(len(li)):
    pass

Could you see that if range() went up to exactly len(li) that this would be problematic? The programmer would need to explicitly subtract 1. This also follows the common trend of programmers preferring for(int i = 0; i < 10; i++) over for(int i = 0; i <= 9; i++).

If you are calling range with a start of 1 frequently, you might want to define your own function:

>>> def range1(start, end):
...     return range(start, end+1)
...
>>> range1(1, 10)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]