Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #30420

RE: data attributes override method attributes?

Show key headers only | View raw

Terry Reedy wrote:
> On 9/25/2012 4:07 PM, Ian Kelly wrote:
> > On Tue, Sep 25, 2012 at 1:58 PM, Terry Reedy <tjreedy@udel.edu> wrote:
> >> On 9/25/2012 11:03 AM, Chris Angelico wrote:
> >>> Instance attributes override (shadow) class attributes.
> >>
> >>
> >> except for (some? all?) special methods
> >
> > Those names are shadowed too.  If you call foo.__len__() and the name
> > is bound on the instance, it will call that function preferentially.
> > It's just that when the special Python machinery calls the method, it
> > skips the instance and goes straight to the class.
> 
> I added "Ian Kelly reminds me that instance.__xxx__ is only skipped by
> the internal machinery and not by direct accesses in user code. In the
> other hand, docs, official or otherwise, are filled with things like
> 'len(a) calls a.__len__', so I think something should be said that
> giving instances special method attributes does not have the effect one
> might expect."
> 
> to the issue.
> 


Just to make sure I am following, if you call
foo.__len__() it goes to the instance code while
if you do len(foo) it will go to class.__len__()?

If so, why? 

This email is confidential and subject to important disclaimers and
conditions including on offers for the purchase or sale of
securities, accuracy and completeness of information, viruses,
confidentiality, legal privilege, and legal entity disclaimers,
available at http://www.jpmorgan.com/pages/disclosures/email.  

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

Thread

data attributes override method attributes? Jayden <jayden.shui@gmail.com> - 2012-09-25 06:41 -0700
  Re: data attributes override method attributes? alex23 <wuwei23@gmail.com> - 2012-09-25 06:52 -0700
  Re: data attributes override method attributes? Peter Otten <__peter__@web.de> - 2012-09-25 16:08 +0200
    Re: data attributes override method attributes? alex23 <wuwei23@gmail.com> - 2012-09-25 07:11 -0700
      Re: data attributes override method attributes? Peter Otten <__peter__@web.de> - 2012-09-25 16:54 +0200
      Re: data attributes override method attributes? Chris Angelico <rosuav@gmail.com> - 2012-09-26 01:03 +1000
      Re: data attributes override method attributes? Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-09-25 16:54 +0200
      Re: data attributes override method attributes? Terry Reedy <tjreedy@udel.edu> - 2012-09-25 15:58 -0400
      Re: data attributes override method attributes? Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-25 14:07 -0600
      Re: data attributes override method attributes? Terry Reedy <tjreedy@udel.edu> - 2012-09-25 16:18 -0400
      Re: data attributes override method attributes? Terry Reedy <tjreedy@udel.edu> - 2012-09-25 16:34 -0400
      RE: data attributes override method attributes? "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-09-28 18:02 +0000
        Re: data attributes override method attributes? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-29 03:20 +0000
      Re: data attributes override method attributes? Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-28 12:25 -0600
      Re: data attributes override method attributes? Terry Reedy <tjreedy@udel.edu> - 2012-09-28 14:26 -0400
    Re: data attributes override method attributes? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-09-25 21:52 +0200
  Re: data attributes override method attributes? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-25 14:12 +0000

csiph-web