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Re: New user's initial thoughts / criticisms of Python

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> On Saturday, November 9, 2013 8:27:02 AM UTC-5, Joshua Landau wrote:
> The C switch statement is very limited.  The select statement
> in the dialect of BASIC I regularly use is more flexible.
> It's more concise on long if chains because it elides the "end
> if"s.  But the use of indentation for blocks and the "in"
> operator certainly reduce the need for it in Python.

It's say the C switch isn't limited enough to be a Python
resident. The default fallthrough, labels, jumps and breaks make
it a poor Python construct.

K&R have this to say: "Falling through from one case to another
is not robust, being prone to disintegration when the program is
modified."

So Python would need something simler. Once you winnow it down to
a robust feature, it provide virtually nothing you don't get with
an if/elif/else. At best it would save a temporary.

> The switch statement in (the language) go is similar, except
> that <expression0> defaults to true and it doesn't elide
> <expression0> in the case statements.

Go makes interesting use of switch statements. In addition to
what you might expect, you can also do type switches. A type
switch lets you provide a different execution path depending on
the underlying object represented by an interface.

Thus, Go carved out a useful niche for a robust switch statement.
Python used duck-typing instead of interfaces and generally
doesn't need any special syntax for type checks, hence Go's
version of switch doesn't make sense for Python, either.

Go's cases must be constants, and allows optional fallthrough
with the 'fallthrough' keyword. This forces them to provide break
semantics to break out of a switch, which makes using them to
break of an immediately outer loop messy.

> Dictionaries can't handle the uses where expression0 is
> constant and the case expressions are not. Function variables
> beg the question.  How did you decide what to assign to the
> variable?

A Python generator might take the place of that application, but
I haven't tried it for that.

> I'd use this select if it was in Python, but I don't see much
> need for it.

Same here. Perhaps the real value of a switch is that it seems to
be a more natural way of thinking about execution. The caveat to
that is most *actual* switch implementations are a mess.

-- 
Neil Cerutti

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Thread

New user's initial thoughts / criticisms of Python John von Horn <j.h69@btinternet.com> - 2013-11-09 07:08 -0600
  Re: New user's initial thoughts / criticisms of Python Ned Batchelder <ned@nedbatchelder.com> - 2013-11-09 05:22 -0800
  Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-09 13:27 +0000
    Re: New user's initial thoughts / criticisms of Python Jonathan <jtcegh@gmail.com> - 2013-11-09 14:44 -0800
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 10:29 +1100
      Re: New user's initial thoughts / criticisms of Python MRAB <python@mrabarnett.plus.com> - 2013-11-10 00:50 +0000
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 11:54 +1100
      Re: New user's initial thoughts / criticisms of Python Neil Cerutti <neilc@norwich.edu> - 2013-11-11 15:30 +0000
    Re: New user's initial thoughts / criticisms of Python Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2013-11-10 13:24 +0100
  Re: New user's initial thoughts / criticisms of Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-09 13:41 +0000
  Re: New user's initial thoughts / criticisms of Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-11-09 16:24 +0200
  Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 01:27 +1100
    Sandboxing Python [was Re: New user's initial thoughts / criticisms of Python] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-09 15:25 +0000
      Re: Sandboxing Python [was Re: New user's initial thoughts / criticisms of Python] Chris Angelico <rosuav@gmail.com> - 2013-11-10 02:32 +1100
    Re: New user's initial thoughts / criticisms of Python Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-11-10 08:47 +0000
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 20:22 +1100
      Re: New user's initial thoughts / criticisms of Python Ian Kelly <ian.g.kelly@gmail.com> - 2013-11-10 04:39 -0700
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-10 22:43 +1100
      Re: New user's initial thoughts / criticisms of Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-11-10 12:12 -0500
      Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 10:29 +1100
      Re: New user's initial thoughts / criticisms of Python Terry Reedy <tjreedy@udel.edu> - 2013-11-10 19:13 -0500
  Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-09 07:38 -0800
    Re: New user's initial thoughts / criticisms of Python Roy Smith <roy@panix.com> - 2013-11-09 10:56 -0500
      Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-09 08:30 -0800
        Re: New user's initial thoughts / criticisms of Python Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-10 21:36 -0800
          Re: New user's initial thoughts / criticisms of Python Roy Smith <roy@panix.com> - 2013-11-11 09:01 -0500
            Re: New user's initial thoughts / criticisms of Python rusi <rustompmody@gmail.com> - 2013-11-11 07:14 -0800
            Re: New user's initial thoughts / criticisms of Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-11-11 21:05 -0500
            Re: New user's initial thoughts / criticisms of Python Ethan Furman <ethan@stoneleaf.us> - 2013-11-12 14:38 -0800
  Re: New user's initial thoughts / criticisms of Python John von Horn <j.h69@btinternet.com> - 2013-11-09 14:19 -0600
  Re: New user's initial thoughts / criticisms of Python Tim Chase <python.list@tim.thechases.com> - 2013-11-09 14:39 -0600
  Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-09 12:33 -0800
    Re: New user's initial thoughts / criticisms of Python Ned Batchelder <ned@nedbatchelder.com> - 2013-11-09 12:54 -0800
      Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-09 13:21 -0800
  Re: New user's initial thoughts / criticisms of Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-09 21:01 +0000
  Re: New user's initial thoughts / criticisms of Python Tim Chase <python.list@tim.thechases.com> - 2013-11-09 15:20 -0600
  Re: New user's initial thoughts / criticisms of Python lorenzo.gatti@gmail.com - 2013-11-11 02:09 -0800
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 21:39 +1100
      Re: New user's initial thoughts / criticisms of Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-11 11:17 +0000
        Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 22:32 +1100
        Re: New user's initial thoughts / criticisms of Python Mark Janssen <dreamingforward@gmail.com> - 2013-11-11 14:29 -0800
    Re: New user's initial thoughts / criticisms of Python Robert Kern <robert.kern@gmail.com> - 2013-11-11 11:53 +0000
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-11 23:07 +1100
    Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-11 20:50 +0000
    Re: New user's initial thoughts / criticisms of Python Chris Angelico <rosuav@gmail.com> - 2013-11-12 09:21 +1100
    Re: New user's initial thoughts / criticisms of Python Joshua Landau <joshua@landau.ws> - 2013-11-12 01:53 +0000

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