Re: functions, optional parameters

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Date	Sat, 9 May 2015 12:05:53 +1000
Subject	Re: functions, optional parameters
From	Chris Angelico <rosuav@gmail.com>
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On Sat, May 9, 2015 at 11:41 AM, Gregory Ewing
<greg.ewing@canterbury.ac.nz> wrote:
> Chris Angelico wrote:
>>
>> How do you know that the function's code
>> object was created when compile() happened, rather than being created
>> when the function was defined?
>
>
> Python 3.4.2 (default, Feb  4 2015, 20:08:25)
> [GCC 4.2.1 (Apple Inc. build 5664)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
>>>> source = "def f(x = 42): pass"
>>>> code = compile(source, "", "exec")
>>>> c1 = code.co_consts[1]
>>>> c1
> <code object f at 0x53d430, file "", line 1>
>>>> e = {}
>>>> exec(code, e)
>>>> c2 = e['f'].__code__
>>>> c2
> <code object f at 0x53d430, file "", line 1>
>>>> c1 is c2
> True
>
> Is that proof enough for you?

That's what I reached for as my first try, but it's no different from this:

>>> def f(x=42): return x + 1
...
>>> n1 = f()
>>> n2 = f(n1-1)
>>> n1 is n2
True

Clearly in this case, the "x + 1" is getting evaluated at run-time,
and yet the interpreter is welcome to intern the constants. So no, it
isn't proof - it's equally well explained by the code object being
constant.

ChrisA

Thread

functions, optional parameters Michael Welle <mwe012008@gmx.net> - 2015-05-08 13:59 +0200
  Re: functions, optional parameters Rustom Mody <rustompmody@gmail.com> - 2015-05-08 05:09 -0700
    Re: functions, optional parameters Michael Welle <mwe012008@gmx.net> - 2015-05-08 14:36 +0200
  Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-08 22:39 +1000
    Re: functions, optional parameters Michael Welle <mwe012008@gmx.net> - 2015-05-08 14:57 +0200
  Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-09 01:24 +1000
    Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-09 02:02 +1000
      Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-09 03:36 +1000
        Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-09 03:49 +1000
          Re: functions, optional parameters Mel Wilson <mwilson@the-wire.com> - 2015-05-08 18:49 +0000
          Re: functions, optional parameters Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-09 13:41 +1200
            Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-09 12:05 +1000
              Re: functions, optional parameters Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-05-09 19:27 +1200
          Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-09 12:52 +1000
    Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-09 03:26 +1000
    Re: functions, optional parameters Michael Welle <mwe012008@gmx.net> - 2015-05-08 17:50 +0200
      Re: functions, optional parameters Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-09 10:57 -0600
      Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-10 13:33 +1000
        Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-10 15:20 +1000
          Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-10 18:59 +1000
      Re: functions, optional parameters Rustom Mody <rustompmody@gmail.com> - 2015-05-09 20:35 -0700
        Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-10 15:25 +1000
      Re: functions, optional parameters Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-10 12:45 +1000
        Re: functions, optional parameters Dave Angel <davea@davea.name> - 2015-05-10 07:25 -0400
        Re: functions, optional parameters Chris Angelico <rosuav@gmail.com> - 2015-05-11 00:39 +1000
        Re: functions, optional parameters Michael Welle <mwe012008@gmx.net> - 2015-05-11 07:58 +0200
    Re: functions, optional parameters Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-08 09:48 -0600

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