[Tutor] more on index handling

[Alan Gauld]

> Question : why does python exclude the last index of a slice ? Below
what I
> mean :
> ************
> >>> l=[1,2,3,4,5]
> >>> l[1:3]
> [2, 3]
> ************
> I would "naturally" expect that l[1:3] returns [1,2,3], but as i
know that
> the indexes are 0-based I expect python to return [2,3,4].

Slices are different :-)
They work like a knife being inserted before the items you specify.
So thinking of

[1,2,3,4,5]

Inset the knife before item 1 and item 3 (at the comma if you like)
and you get [2,3]...

Why? Dunno, but it's consistent with the range function

range(1,3)

returns [1,2] not [1,2,3]

and slicing [0,1,2,3] with [1:3} returns [1,2] the same as range.

So you can think of range as a type of slicing function...

No it's not very convincing is it?! :-)

Alan G.