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Re: Enchancement suggestion for argparse: intuit type from default

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Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:

> On Wed, 14 Mar 2012 08:35:12 +1100, Ben Finney wrote:
> > That feels too magical to me. I don't see a need to special-case
> > that usage. There's not much burden in being explicit for the
> > argument type.
>
> And yet you are programming in Python instead of Java, Pascal or Ada
> :)

That's a good point :-)

> It's not magic at all, it's science! Or to be precise, it's a very simple 
> form of type inference

Right. I dislike proposals for run-time type inference in Python, since
they are too magical.

Especially since we're talking about user input (arguments from the
command line to the program); that requires more explicit declarations
and checking, not less.

> What if you want an argument --foo that will accept arbitrary types? Then 
> you would need some way to tell argparse not to infer the type from the 
> default.

So we would then need to special-case the special-case? Even more reason
to dislike this proposal.

> Explicit declarations should be used only for the uncommon cases where
> type inference cannot cope.

That's our point of disagreement, then: I think explicit declarations
should be required regarding user input.

-- 
 \              “Ridicule is the only weapon which can be used against |
  `\       unintelligible propositions.” —Thomas Jefferson, 1816-07-30 |
_o__)                                                                  |
Ben Finney

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Thread

Enchancement suggestion for argparse: intuit type from default roy@panix.com (Roy Smith) - 2012-03-13 17:08 -0400
  Re: Enchancement suggestion for argparse: intuit type from default Ben Finney <ben+python@benfinney.id.au> - 2012-03-14 08:35 +1100
    Re: Enchancement suggestion for argparse: intuit type from default Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-03-14 12:53 +0000
      Re: Enchancement suggestion for argparse: intuit type from default Ben Finney <ben+python@benfinney.id.au> - 2012-03-15 00:19 +1100
        Re: Enchancement suggestion for argparse: intuit type from default Roy Smith <roy@panix.com> - 2012-03-14 09:30 -0400
          Re: Enchancement suggestion for argparse: intuit type from default MRAB <python@mrabarnett.plus.com> - 2012-03-14 17:26 +0000
          Re: Enchancement suggestion for argparse: intuit type from default Ian Kelly <ian.g.kelly@gmail.com> - 2012-03-14 13:03 -0600
  Re: Enchancement suggestion for argparse: intuit type from default rusi <rustompmody@gmail.com> - 2012-03-14 03:22 -0700
  Re: Enchancement suggestion for argparse: intuit type from default Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-03-14 13:26 +0100
  Re: Enchancement suggestion for argparse: intuit type from default John Nagle <nagle@animats.com> - 2012-03-14 16:32 -0700
    Re: Enchancement suggestion for argparse: intuit type from default Roy Smith <roy@panix.com> - 2012-03-14 20:52 -0400
      Re: Enchancement suggestion for argparse: intuit type from default Ben Finney <ben+python@benfinney.id.au> - 2012-03-15 12:22 +1100
        Re: Enchancement suggestion for argparse: intuit type from default Cameron Simpson <cs@zip.com.au> - 2012-03-15 16:59 +1100
        Re: Enchancement suggestion for argparse: intuit type from default Robert Kern <robert.kern@gmail.com> - 2012-03-15 10:06 +0000
          Re: Enchancement suggestion for argparse: intuit type from default Roy Smith <roy@panix.com> - 2012-03-15 09:28 -0400
            Re: Enchancement suggestion for argparse: intuit type from default Cameron Simpson <cs@zip.com.au> - 2012-03-16 08:18 +1100
      Re: Enchancement suggestion for argparse: intuit type from default MRAB <python@mrabarnett.plus.com> - 2012-03-15 02:10 +0000

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