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Groups > comp.lang.python > #69612

Re: Default mutable parameters in functions

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On Thu, Apr 3, 2014 at 12:49 PM,  <fbicknel@gmail.com> wrote:
> Now call it with a value:
> foo([ 3 ])
>
> as you might expect:
> It's a parrot, not a cheese: [3]
>
> But now go back to no parameter in the call:
> foo()
> foo()
> foo()
>
> It's a parrot, not a cheese: [46]
> It's a parrot, not a cheese: [47]
> It's a parrot, not a cheese: [48]
>
> it picks up where it left off.
>
> I was rather expecting it to start with 4!

You haven't replaced the default value; you've only substituted a
different value for that call.  In this function:

def foo(x=3):
    print(x)

You wouldn't expect a call of foo(27) to change the default value to
27, would you?

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Default mutable parameters in functions fbicknel@gmail.com - 2014-04-03 11:49 -0700
  Re: Default mutable parameters in functions Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-03 15:32 -0600
  Re: Default mutable parameters in functions Ethan Furman <ethan@stoneleaf.us> - 2014-04-03 14:44 -0700
  Re: Default mutable parameters in functions Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-03 20:27 -0400
  Re: Default mutable parameters in functions Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-04 01:38 +0100
  Re: Default mutable parameters in functions random832@fastmail.us - 2014-04-04 10:00 -0400
    Re: Default mutable parameters in functions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-04 14:34 +0000
      Re: Default mutable parameters in functions Chris Angelico <rosuav@gmail.com> - 2014-04-05 09:47 +1100
  Re: Default mutable parameters in functions Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-04-04 19:23 -0400
    Re: Default mutable parameters in functions Roy Smith <roy@panix.com> - 2014-04-04 19:38 -0400
  Re: Default mutable parameters in functions Dave Angel <davea@davea.name> - 2014-04-04 22:21 -0400

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