[Tutor] list semantics

[Steven D'Aprano]

On Sat, Apr 11, 2015 at 10:41:28AM -0700, Jim Mooney wrote:
> Why does the first range convert to a list, but not the second?
> 
> >>> p = list(range(1,20)), (range(40,59))
> >>> p
> ([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19],
>  range(40, 59))

Why would the second convert to a list? You don't call list() on it.

You create a tuple, p, with two items. The first item is:

list(range(1, 20))

and the second item is:

range(40, 59)

so you end up with p being a tuple ([1, 2, 3, ..., 19], range(40, 59)).

The fact that you surround the second item with round brackets 
(parentheses) means nothing -- they just group the range object on its 
own. A bit like saying 1 + (2), which still evaluates as 3.



-- 
Steve