Re: Encapsulation in Python

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.python
Subject	Re: Encapsulation in Python
Date	2016-03-15 01:22 +0000
Organization	A noiseless patient Spider
Message-ID	<nc7nuv$sgd$1@dont-email.me> (permalink)
References	(13 earlier) <mailman.137.1457997645.12893.python-list@python.org> <nc7it9$ejq$1@dont-email.me> <mailman.138.1458000749.12893.python-list@python.org> <nc7man$obt$1@dont-email.me> <mailman.147.1458003523.12893.python-list@python.org>

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On 15/03/2016 00:58, Chris Angelico wrote:
> On Tue, Mar 15, 2016 at 11:54 AM, BartC <bc@freeuk.com> wrote:
>>> In Python, there's no reason to restrict 'switch'
>>> to integers, so I would expect its semantics to be based on either
>>> equality comparisons or inequality comparisons
>>
>>
>> I use two forms of switch: one for integers only (very fast), and the other
>> for any other values, which does tests in sequence.
>
> I'm not sure what you gain by restricting to integers that you
> couldn't also gain with other hashable types. Can you elaborate on
> these optimizations?

The integer-switch is intended for use with jump-tables, which requires 
not only that the case expressions are known at compile-time, but that 
they don't span too large a range.

(When a jump-table couldn't be used, then there was a slightly different 
implementation which scanned a list of the case-expressions. Linearly; a 
binary search or hash look-up could be done too, but this was in fast 
static code, not interpreted, so was not too critical. But I don't use 
this any more anyway.)

For use with Python, because constant expressions are going to be 
limited, such a switch would only work with case expressions that are 
numeric literals or character constants, which have to be written 
b"A"[0] iirc. So rather limited unless someone introduces named 
constants at the same time...

-- 
Bartc

Thread

Re: Encapsulation in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-10 08:27 -0700
  Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-10 16:45 -0800
    Re: Encapsulation in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-11 08:47 -0700
      Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-11 18:39 -0800
        Re: Encapsulation in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-12 09:44 -0700
          Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-12 19:11 -0800
          Re: Encapsulation in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-13 21:11 +1100
            Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-14 10:32 -0700
              Re: Encapsulation in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-14 15:09 -0600
              Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-14 21:23 +0000
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-14 22:07 +0000
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-14 22:20 +0000
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-14 22:40 +0000
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-14 23:19 +0000
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-14 23:56 +0000
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 11:12 +1100
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-15 00:54 +0000
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 11:58 +1100
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-15 01:22 +0000
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 13:02 +1100
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-15 00:28 +0000
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-15 01:10 +0000
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 12:23 +1100
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-15 04:41 +0000
                Re: Encapsulation in Python rurpy@yahoo.com - 2016-03-14 17:17 -0700
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 11:25 +1100
                Re: Encapsulation in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-15 13:06 +1100
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 13:14 +1100
                Re: Encapsulation in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-15 13:40 +1100
                Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-14 21:08 -0700
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-15 00:47 +0000
                Re: Encapsulation in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-15 13:46 +1100
                Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-15 11:56 +1100
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-15 04:36 +0000
                Re: Encapsulation in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-15 13:01 +1100
                Re: Encapsulation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-15 04:45 +0000
                Re: Encapsulation in Python Christian Gollwitzer <auriocus@gmx.de> - 2016-03-15 22:02 +0100
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-16 00:39 +0000
                Re: Encapsulation in Python BartC <bc@freeuk.com> - 2016-03-16 22:58 +0000
        Re: Encapsulation in Python sohcahtoa82@gmail.com - 2016-03-14 11:11 -0700
          Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-14 23:09 -0700
      Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-11 18:56 -0800
    Re: Encapsulation in Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-03-12 13:52 +1300
      Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-12 08:49 -0800
        Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-13 08:10 +1100
          Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-12 19:36 -0800
            Re: Encapsulation in Python Chris Angelico <rosuav@gmail.com> - 2016-03-13 15:05 +1100
        Re: Encapsulation in Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-03-14 12:35 +1300
          Re: Encapsulation in Python Rick Johnson <rantingrickjohnson@gmail.com> - 2016-03-14 15:55 -0700

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