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Re: How to run script from interpreter?

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On Fri, May 30, 2014 at 9:27 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> This is why I'm so adamant that, while REPLs may be permitted to
> introduce *new* syntax which is otherwise illegal to the Python parser,
> (e.g. like IPython's %magic and !shell commands) they *must not* change
> the meaning of otherwise legal Python syntax. It's simply a bad idea to
> have legal Python code mean different things depending on what
> environment you're running it in.

Hmm. I'm not sure that "raises SyntaxError" is any less a part of the
language's promise than "evaluates to twice the value of x" is. Would
you, for instance, permit the REPL to define a new __future__
directive, on the basis that it's invalid syntax currently?

>>> from __future__ import magic_command_history
SyntaxError: future feature magic_command_history is not defined

I don't think SyntaxError equates to "invitation to make changes".
Also, consider:

>>> for i in range(5): i*3+2

2
5
8
11
14

If you do this in a script, it's perfectly legal, but won't print
anything. So the REPL is already "chang[ing] the meaning of otherwise
legal Python syntax", and what's more, it's making None into a special
case:

>>> for i in range(5): None if i%2 else i

0
2
4

Practicality beats purity. If it's more useful to the end user for
something valid-but-illogical to have a new bit of meaning in
interactive mode, I say go for it.

ChrisA

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Re: How to run script from interpreter? onlyvinish@gmail.com - 2014-05-28 00:44 -0700
  Re: How to run script from interpreter? Terry Reedy <tjreedy@udel.edu> - 2014-05-28 11:32 -0400
  Re: How to run script from interpreter? Mark H Harris <harrismh777@gmail.com> - 2014-05-28 11:39 -0500
    Re: How to run script from interpreter? Steven D'Aprano <steve@pearwood.info> - 2014-05-29 03:22 +0000
      Re: How to run script from interpreter? Mark H Harris <harrismh777@gmail.com> - 2014-05-29 15:26 -0500
        Re: How to run script from interpreter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-30 00:33 +0000
          Re: How to run script from interpreter? Chris Angelico <rosuav@gmail.com> - 2014-05-30 10:46 +1000
            Re: How to run script from interpreter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-30 01:49 +0000
              Re: How to run script from interpreter? Chris Angelico <rosuav@gmail.com> - 2014-05-30 12:04 +1000
                Re: How to run script from interpreter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-30 06:20 +0000
                Re: How to run script from interpreter? Chris Angelico <rosuav@gmail.com> - 2014-05-30 17:19 +1000
                Re: How to run script from interpreter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-30 11:27 +0000
                Re: How to run script from interpreter? Chris Angelico <rosuav@gmail.com> - 2014-05-30 21:46 +1000
                Re: How to run script from interpreter? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-05-30 19:28 +0000
                Re: How to run script from interpreter? Chris Angelico <rosuav@gmail.com> - 2014-05-31 05:47 +1000
                Re: How to run script from interpreter? Terry Reedy <tjreedy@udel.edu> - 2014-05-30 11:24 -0400

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