Ad hoc lists vs ad hoc tuples
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From: Floris Bruynooghe on 27 Jan 2010 05:20 One thing I ofter wonder is which is better when you just need a throwaway sequence: a list or a tuple? E.g.: if foo in ['some', 'random', 'strings']: ... if [bool1, bool2, boo3].count(True) != 1: ... (The last one only works with tuples since python 2.6) Is a list or tuple better or more efficient in these situations? Regards Floris PS: This is inspired by some of the space-efficiency comments from the list.pop(0) discussion.
From: Iain King on 27 Jan 2010 07:22 On Jan 27, 10:20 am, Floris Bruynooghe <floris.bruynoo...(a)gmail.com> wrote: > One thing I ofter wonder is which is better when you just need a > throwaway sequence: a list or a tuple? E.g.: > > if foo in ['some', 'random', 'strings']: > ... > if [bool1, bool2, boo3].count(True) != 1: > ... > > (The last one only works with tuples since python 2.6) > > Is a list or tuple better or more efficient in these situations? > > Regards > Floris > > PS: This is inspired by some of the space-efficiency comments from the > list.pop(0) discussion. I tend to use tuples unless using a list makes it easier to read. For example: if foo in ('some', 'random', 'strings'): draw.text((10,30), "WHICH IS WHITE", font=font) draw.line([(70,25), (85,25), (105,45)]) I've no idea what the performance difference is; I've always assumed it's negligible. Iain
From: M.-A. Lemburg on 27 Jan 2010 09:47 Iain King wrote: > On Jan 27, 10:20 am, Floris Bruynooghe <floris.bruynoo...(a)gmail.com> > wrote: >> One thing I ofter wonder is which is better when you just need a >> throwaway sequence: a list or a tuple? E.g.: >> >> if foo in ['some', 'random', 'strings']: >> ... >> if [bool1, bool2, boo3].count(True) != 1: >> ... >> >> (The last one only works with tuples since python 2.6) >> >> Is a list or tuple better or more efficient in these situations? >> >> Regards >> Floris >> >> PS: This is inspired by some of the space-efficiency comments from the >> list.pop(0) discussion. > > I tend to use tuples unless using a list makes it easier to read. For > example: > > if foo in ('some', 'random', 'strings'): > > draw.text((10,30), "WHICH IS WHITE", font=font) > draw.line([(70,25), (85,25), (105,45)]) > > I've no idea what the performance difference is; I've always assumed > it's negligible. Tuples are a faster to create than lists, so if you create lots of them and don't need the list features, use tuples. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Jan 27 2010) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ ::: Try our new mxODBC.Connect Python Database Interface for free ! :::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 http://www.egenix.com/company/contact/
From: Steve Holden on 27 Jan 2010 10:18 Iain King wrote: > On Jan 27, 10:20 am, Floris Bruynooghe <floris.bruynoo...(a)gmail.com> > wrote: >> One thing I ofter wonder is which is better when you just need a >> throwaway sequence: a list or a tuple? E.g.: >> >> if foo in ['some', 'random', 'strings']: >> ... >> if [bool1, bool2, boo3].count(True) != 1: >> ... >> >> (The last one only works with tuples since python 2.6) >> >> Is a list or tuple better or more efficient in these situations? >> >> Regards >> Floris >> >> PS: This is inspired by some of the space-efficiency comments from the >> list.pop(0) discussion. > > I tend to use tuples unless using a list makes it easier to read. For > example: > > if foo in ('some', 'random', 'strings'): > > draw.text((10,30), "WHICH IS WHITE", font=font) > draw.line([(70,25), (85,25), (105,45)]) > > I've no idea what the performance difference is; I've always assumed > it's negligible. > The fact that you have felt able to neglect the performance difference makes it quite literally negligible. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 PyCon is coming! Atlanta, Feb 2010 http://us.pycon.org/ Holden Web LLC http://www.holdenweb.com/ UPCOMING EVENTS: http://holdenweb.eventbrite.com/
From: Antoine Pitrou on 27 Jan 2010 12:32
Le Wed, 27 Jan 2010 02:20:53 -0800, Floris Bruynooghe a écrit : > > Is a list or tuple better or more efficient in these situations? Tuples are faster to allocate (they are allocated in one single step) and quite a bit smaller too. In some situations, in Python 2.7 and 3.1, they can also be ignored by the garbage collector, yielding faster collections. (not to mention that they are hashable, which can be useful) |