Grabbing previous iteration in a dict

[Hyuga]

On May 9, 5:10 am, dannywebs... at googlemail.com wrote:
> 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.

Why is that so terrible?
previous = None
for key in mydict:
    if key.starswith('foo') and previous is not None:
        # ...do stuff...
    previous = key

Doesn't seem too ugly to me.

> Is there a mechanism whereby I can just index the dict value
> subscripts like in an array? I could just rewind by 1 if so.

You can't rely on the keys in a dictionary being in any specific
order.  But if you want a list of the keys you can just call
mydict.keys() which will give a copy of the dictionary's keys in a
list.  Then you can iterate that and use it however you would use any
other list.  Note that it's a copy though.  It might help if you
better explained exactly what you need to do.