advice : how do you iterate with an acc ?

[Scott David Daniels]

Jeffrey Schwab wrote:
> vd12005 at yahoo.fr wrote:
>> hello,
>>
>> .... i often encounter something like:
>>
>> acc = []    # accumulator ;)
>> for line in fileinput.input():
>>     if condition(line):
>>         if acc:    #1
>>             doSomething(acc)    #1
>>         acc = []
>>     else:
>>         acc.append(line)
>> if acc:    #2
>>     doSomething(acc)    #2
> 
> Could you add a sentry to the end of your input?  E.g.:
>     for line in fileinput.input() + line_that_matches_condition:
> This way, you wouldn't need a separate check at the end.

Check itertools for a good way to do this:

     import itertools
     SENTRY = 'something for which condition(SENTRY) is True'

     f = open(filename)
     try:
         for line in itertools.chain(f, [SENTRY]):
             if condition(line):
                 if acc:
                     doSomething(acc)
                 acc = []
             else:
                 acc.append(line)
         assert acc == []
     finally:
         f.close()


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