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Re: Deep vs. shallow copy?

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On Fri, Mar 14, 2014 at 10:41 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> Are you trolling again?
>
> I'm sure that you know quite well that Python doesn't have a procedure
> type. It uses a single keyword, def, for creating both functions and
> functions-that-return-None.

I'm going to troll for a moment and give you a function that has no
return value.

def procedure():
    raise Exception

But seriously, this is something that some functions do when they need
to distinguish between returning something and not returning anything.
Look at a dictionary's subscripting (which is effectively a function
call):

>>> x={1:2}
>>> x[1]
2
>>> x[3]
Traceback (most recent call last):
  File "<pyshell#17>", line 1, in <module>
    x[3]
KeyError: 3

It can't return None to indicate "there was no such key in the
dictionary", so it raises instead. There's only one way for a Python
function to not have a return value: it has to not return.

ChrisA

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Thread

Deep vs. shallow copy? Alex van der Spek <zdoor@xs4all.nl> - 2014-03-12 14:25 +0000
  Re: Deep vs. shallow copy? Skip Montanaro <skip@pobox.com> - 2014-03-12 09:48 -0500
  Re: Deep vs. shallow copy? Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-03-12 10:00 -0500
    Re: Deep vs. shallow copy? Alex van der Spek <zdoor@xs4all.nl> - 2014-03-12 15:29 +0000
      Re: Deep vs. shallow copy? Wayne Brehaut <wbrehaut@mcsnet.ca> - 2014-03-12 13:06 -0600
      Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-12 23:07 +0000
        Re: Deep vs. shallow copy? Rustom Mody <rustompmody@gmail.com> - 2014-03-12 20:09 -0700
          Re: Deep vs. shallow copy? Ian <hobson42@gmail.com> - 2014-03-13 11:38 +0000
            Re: Deep vs. shallow copy? Rustom Mody <rustompmody@gmail.com> - 2014-03-13 08:28 -0700
              Re: Deep vs. shallow copy? random832@fastmail.us - 2014-03-13 13:25 -0400
        Re: Deep vs. shallow copy? Roy Smith <roy@panix.com> - 2014-03-13 07:44 -0400
          Re: Deep vs. shallow copy? Marko Rauhamaa <marko@pacujo.net> - 2014-03-13 14:27 +0200
            Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-13 23:41 +0000
              Re: Deep vs. shallow copy? Chris Angelico <rosuav@gmail.com> - 2014-03-14 10:55 +1100
                Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-14 01:41 +0000
              Re: Deep vs. shallow copy? Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-13 18:08 -0600
              Re: Deep vs. shallow copy? Chris Angelico <rosuav@gmail.com> - 2014-03-14 11:22 +1100
                Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-14 01:59 +0000
              Re: Deep vs. shallow copy? Rustom Mody <rustompmody@gmail.com> - 2014-03-13 19:57 -0700
                Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-14 04:43 +0000
              Re: Deep vs. shallow copy? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-14 06:17 +0000
          Re: Deep vs. shallow copy? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-13 23:31 +0000

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