In need of a binge-and-purge idiom

[Magnus Lie Hetland]

In article <mailman.1048447384.30411.python-list at python.org>, Tim Peters wrote:
>[Magnus Lie Hetland]
>> Maybe not the best name, but it somehow describes what's going on...
>> So...
>>
>> I've noticed that I use the following in several contexts:

A little fix...

>>   chunk = []
>>   for element in iterable:
>>       if isSeparator(element):
             if chunk:
>>               doSomething(chunk)
>>               chunk = []
         else:
             chunk.append(element)
>>   if chunk:
>>       doSomething(chunk)
>>       chunk = []

The original was written in a hurry :]

>Since chunk is initialized to an empty list, the if clause in the loop can
>never evaluate to true, so this is equivalent to
>
>    chunk = []
>    for element in iterable:
>        isSeparator(element)

Yup.

>All variations of the code later in the msg suffer the same problem.  As a
>result, I've got no idea what you intend the code to do.  Does calling
>isSeparator(element), or <shudder> the process of iterating over iterable,
>mutate chunk as a side effect?  If so, "yuck" comes to mind.

No, sorry -- I just forgot parts of the code :)

>If the code made sense <wink>, something like
>
>def terminated_iterator(iterable, a_seperator):
>    for element in iterable:
>        yield element
>    yield a_separator
>
>would produce the original sequence, then tack a_separator on to the end.

Yes, that's what I've done before (e.g. in an example in my book).
Maybe that is the best way of doing it.

[snip]
>WRT the preceding,
>
>    for element in terminated_iterator(iterable, seperator):
>
>gets that effect.

Indeed.

>  More generally,
>
>def concat(*seqs):
>    "Generate all the elements of all the argument iterables."
>    for seq in seqs:
>        for x in seq:
>            yield x
>
>and then, e.g.,
>
>    for element in concat(iterable, [seperator]):

Yes. I posted something similar to that when discussing itertools
previously. I guess I was (now) mainly looking for some basic use of
control structures that I had overlooked.

Anyway, thanks for the input.

-- 
Magnus Lie Hetland               "Nothing shocks me. I'm a scientist." 
http://hetland.org                                   -- Indiana Jones