is there a better way?

[Scott David Daniels]

Scott David Daniels wrote:
> markscala at gmail.com wrote:
>> Problem:
>>
>> You have a list of unknown length, such as this: list =
>> [X,X,X,O,O,O,O].  You want to extract all and only the X's.  You know
>> the X's are all up front and you know that the item after the last X is
>> an O, or that the list ends with an X.  There are never O's between
>> X's.
>>
>> I have been using something like this:
>> while list[0] != O:
>>     storage.append(list[0])
>>     list.pop(0)
>>     if len(list) == 0:
>>         break
>> But this seems ugly to me, and using "while" give me the heebies.  Is
>> there a better approach?
>>
> 
> Your names could be better as someone mentioned.
>     ex, oh = 7, 13   # for example
>     data = [ex, ex, ex, oh, oh, oh, oh]
> If you need a list distinct from the original:
>     try:
>         result = data[: data.index(oh)]
>     except ValueError:
>         result = list(data)
> 
> Or you could simply:
>     try:
>         data = data[: data.index(oh)]
>     except ValueError:
>         pass
> and data will be either the sublist you want or the original list.

I forgot the obvious:

     result = data.count(ex) * [ex]

-- 
-Scott David Daniels
scott.daniels at acm.org