Re: groupby behaviour

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.python
Subject	Re: groupby behaviour
Date	2013-02-26 09:35 -0800
Organization	Nightsong/Fort GNOX
Message-ID	<7xhakzvuzp.fsf@ruckus.brouhaha.com> (permalink)
References	<CAF_E5JasO841FBst9EtXJJEQkK54UELgBcAZk8GVyGHigxu8TQ@mail.gmail.com> <CALwzidkatUmAyR06VwdqBr1MH=AbeNhxwzMufkREo3SRa_AbLg@mail.gmail.com> <mailman.2557.1361898573.2939.python-list@python.org>

Show all headers | View raw

andrea crotti <andrea.crotti.0@gmail.com> writes:
> It's very weird though this sharing and still doesn't really look
> rightl, is it done just for performance reasons?

It could consume unbounded amounts of memory otherwise.  E.g. if there
are millions of items in the group.

If you're not worried about that situation it's simplest to just
convert each group to a list for processing it:

   for k,g in groupby(...):
      gs = list(g)
      # do stuff with gs

calling list(g) reads all the elements in the group, advancing groupby's
internal iterator to the next group.  Since you've copied out all the
group elements, you don't have to worry about the sharing effect.

Back to comp.lang.python | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: groupby behaviour andrea crotti <andrea.crotti.0@gmail.com> - 2013-02-26 17:09 +0000
  Re: groupby behaviour Paul Rubin <no.email@nospam.invalid> - 2013-02-26 09:35 -0800

csiph-web