[docs] sum()

[bob gailer]

Currently:

sum(iterable[, start])
Sums start and the items of an iterable from left to right and returns 
the total. start defaults to 0. The iterable‘s items are normally 
numbers, and the start value is not allowed to be a string

I just learned that

sum([[1,2],[3,4]],[])
produces:
[1, 2, 3, 4]

I would never have guessed that from the explanation above! I think the 
terms "sum" and "total" are misleading.

apply(operator.add, [[1,2], [3,4]]) generates the same result, but 
emphasizes the use of +.

I suggest either explaining this explicitly or providing an example.

-- 
Bob Gailer
919-636-4239
Chapel Hill NC