Grabbing previous iteration in a dict

[Gary Herron]

dannywebster at googlemail.com wrote:
> On May 9, 10:48 am, Paul Rubin <http://phr...@NOSPAM.invalid> wrote:
>   
>> dannywebs... at googlemail.com writes:
>>     
>>> I have a dictionary of which i'm itervalues'ing through, and i'll be
>>> performing some logic on a particular iteration when a condition is
>>> met with trusty .startswith('foo').  I need to grab the previous
>>> iteration if this condition is met.  I can do something with an extra
>>> var to hold every iteration while iterating, but this is hacky and not
>>> elegant.
>>>       
>> You cannot rely on the elements of a dictionary being in any
>> particular order (dicts are internally hash tables), so the above
>> is almost certainly ont what you want.
>>     
>
>
> Hi - thanks for your reply.  How about if I made the dict into a list
> (of
> which I have done).  How would I then reference the previous item?
> Can they
> be indexed?
> --
> http://mail.python.org/mailman/listinfo/python-list
>   
Yes:

listOfItems = DICT.items()
for i in range(len(listOfItems)):
    k,v = listOfItems[i] # Current key,value pair
    if whatever:
        kPrev,vPrev = listOfItems[i-1]   # Previous key,value pair

Still, since there is no proscribed order in which the items are placed 
into the list, I wonder how this can be useful.   However, this *does* 
do what you asked.

Gary Herron