Pythonic infinite for loop?

John Connor john.theman.connor at gmail.com
Fri Apr 15 04:41:19 CEST 2011


If I understand  your question correctly, what you want is probably
something like:

i = 0
lst=[]
while True:
 try:
   lst.append(parse_kwdlist(dct["Keyword%d"%i]))
   i += 1
 except KeyError:
   break

--jac

On Thu, Apr 14, 2011 at 9:10 PM, Chris Angelico <rosuav at gmail.com> wrote:
> Apologies for interrupting the vital off-topic discussion, but I have
> a real Python question to ask.
>
> I'm doing something that needs to scan a dictionary for elements that
> have a particular beginning and a numeric tail, and turn them into a
> single list with some processing. I have a function parse_kwdlist()
> which takes a string (the dictionary's value) and returns the content
> I want out of it, so I'm wondering what the most efficient and
> Pythonic way to do this is.
>
> My first draft looks something like this. The input dictionary is
> called dct, the output list is lst.
>
> lst=[]
> for i in xrange(1,10000000): # arbitrary top, don't like this
>  try:
>    lst.append(parse_kwdlist(dct["Keyword%d"%i]))
>  except KeyError:
>    break
>
> I'm wondering two things. One, is there a way to make an xrange object
> and leave the top off? (Sounds like I'm risking the numbers
> evaporating or something.) And two, can the entire thing be turned
> into a list comprehension or something? Generally any construct with a
> for loop that appends to a list is begging to become a list comp, but
> I can't see how to do that when the input comes from a dictionary.
>
> In the words of Adam Savage: "Am I about to feel really, really stupid?"
>
> Thanks in advance for help... even if it is just "hey you idiot, you
> forgot about X"!
>
> Chris Angelico
> --
> http://mail.python.org/mailman/listinfo/python-list
>



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