Why don't optional mutable objects show up in vars(func)?

[Fredrik Lundh]

Sean Hammond wrote:

>>>>> def func(x, y=[]):
>> ...     y.append(x)
>> ...     print y
>> ...
>>
>> y is initialized when the function is imported, not when the function
>> is executed.
> 
> I thought it was initialised the first time the function gets called?

it's initialized (in the surrounding context) when the "def" statement 
is executed.

</F>