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Groups > comp.lang.python > #40821

Re: Interesting list() un-optimization

From Terry Reedy <tjreedy@udel.edu>
Subject Re: Interesting list() un-optimization
Date 2013-03-07 15:34 -0500
References <roy-572C99.22201106032013@70-1-84-166.pools.spcsdns.net> <20130306215735.649932ee@bigbox.christie.dr> <loom.20130307T121601-338@post.gmane.org> <CALwzid=wNNBa6Mnx0sr84N1+PiZHMHtra7iQHg_2pYDpsd4kig@mail.gmail.com> <khaep0$qst$1@ger.gmane.org>
Newsgroups comp.lang.python
Message-ID <mailman.3053.1362688500.2939.python-list@python.org> (permalink)

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On 3/7/2013 11:20 AM, Christian Heimes wrote:

> But iterators have a length hint method that are used for some
> optimizations and preallocations, too.

This is easy when the base iterable has a length method, as do range 
objects.

>>>> i = iter(range(10))
>>>> i.__length_hint__()
> 10

And the length_hint can (should be) decremented with each next call.

 >>> next(i); next(i)
0
1
 >>> i.__length_hint__()
8

-- 
Terry Jan Reedy

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Thread

Interesting list() un-optimization Roy Smith <roy@panix.com> - 2013-03-06 22:20 -0500
  Re: Interesting list() un-optimization Dave Angel <davea@davea.name> - 2013-03-06 22:38 -0500
  Re: Interesting list() un-optimization Tim Chase <python.list@tim.thechases.com> - 2013-03-06 21:57 -0600
  Re: Interesting list() un-optimization Kev Dwyer <kevin.p.dwyer@gmail.com> - 2013-03-07 07:31 +0000
  Re: Interesting list() un-optimization Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de> - 2013-03-07 11:22 +0000
  Re: Interesting list() un-optimization Ian Kelly <ian.g.kelly@gmail.com> - 2013-03-07 09:00 -0700
  Re: Interesting list() un-optimization Christian Heimes <christian@python.org> - 2013-03-07 17:20 +0100
  Re: Interesting list() un-optimization Ian Kelly <ian.g.kelly@gmail.com> - 2013-03-07 10:31 -0700
  Re: Interesting list() un-optimization Stefan Behnel <stefan_ml@behnel.de> - 2013-03-07 20:19 +0100
  Re: Interesting list() un-optimization Ian Kelly <ian.g.kelly@gmail.com> - 2013-03-07 13:26 -0700
  Re: Interesting list() un-optimization Terry Reedy <tjreedy@udel.edu> - 2013-03-07 15:29 -0500
  Re: Interesting list() un-optimization Terry Reedy <tjreedy@udel.edu> - 2013-03-07 15:34 -0500
  Re: Interesting list() un-optimization Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de> - 2013-03-07 20:41 +0000
  Re: Interesting list() un-optimization Terry Reedy <tjreedy@udel.edu> - 2013-03-07 17:53 -0500
  Re: Interesting list() un-optimization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-03-08 17:59 +0000
    Re: Interesting list() un-optimization Roy Smith <roy@panix.com> - 2013-03-08 13:45 -0500
  Re: Interesting list() un-optimization Roy Smith <roy@panix.com> - 2013-03-10 09:05 -0400
    Re: Interesting list() un-optimization Terry Reedy <tjreedy@udel.edu> - 2013-03-10 17:39 -0400
      Re: Interesting list() un-optimization Roy Smith <roy@panix.com> - 2013-03-10 18:34 -0400
        Re: Interesting list() un-optimization Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-03-10 23:35 +0000
          Re: Interesting list() un-optimization Roy Smith <roy@panix.com> - 2013-03-10 19:50 -0400

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