Returning a result from 3 items in a list

[Peter Otten]

Cai Gengyang wrote:

> Here's a dictionary with 3 values :
> 
> results = {
>   "gengyang": 14,
>   "ensheng": 13,
>   "jordan": 12
> }
> 
> How do I define a function that takes the last of the 3 items in that list
> and returns Jordan's results i.e. (12) ?
> 
> Thanks a lot !

You can access the last item in a *list* with items[-1]:

>>> results = [
... ("gengyang", 14),
... ("ensheng", 13),
... ("jordan", 12)
... ]
>>> results[-1]
('jordan', 12)

A *dict* is unordered (the order is undefined, to be exact), so there is no 
"last" item. For the rare case when you need both order and fast lookup 
there's collections.OrderedDict:

>>> results = collections.OrderedDict([
... ("gengyang", 14),
... ("ensheng", 13),
... ("jordan", 12)
... ])

Get the last value non-destructively:

>>> results[next(reversed(results))] # is there a less tedious way?
12

Get the last pair, removing it from the dictionary:

>>> results.popitem(last=True)
('jordan', 12)
>>> "jordan" in results
False