Something in the function tutorial confused me.

[Steve Holden]

Marc 'BlackJack' Rintsch wrote:
> On Mon, 06 Aug 2007 10:51:20 -0700, Lee Fleming wrote:
> 
>> why isn't the y in def f (x, y = []): something
>> garbage-collected?
> 
> `y` is a name.  Only objects are garbage collected.  There is no `y` in
> that ``def`` in the sense that a local name `y` exists when the ``def`` is
> executed.  The line just says there will be a local name `y` if
> the function `f()` is executed and that local name will be bound to the
> given object.

Unless the user provides a value for the argument in the call.

>                 Which happen to be a list.  This list is referenced by the
> function object, so it won't get garbage collected, and it is bound to a
> local name `y` every time the function is called.  It is always the
> very same list object.  And if you mutate it, this will be visible to
> other calls to the function.
> 
regards
  Steve
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