[Python-ideas] proto-PEP: Fixing Non-constant Default Arguments

[Georg Brandl]

Roman Susi schrieb:
> Chris Rebert wrote:
>> Jim Jewett wrote:
>> 
>>>On 1/28/07, Chris Rebert <cvrebert at gmail.com> wrote:
> 
> /skip/
> 
>>>
>>>>     def foo(bar=new baz):
>>>>         #code
>>>
>>>This would be less bad.
>>>
>>>That said, I fear many new programmers would fail to understand when
>>>they needed new and when they didn't, so that in practice, it would be
>>>just optional random noise.
>> 
>> 
>> This is part of the reason I'm trying to avoid adding new syntax. 
>> However, I assert that at least 'new' is clearer than the' x=None; if x 
> 
> But if you are concerned with the current None, there could be some
> other, new False value serving the same need, like:
> 
>     def foo(x, y, z, bar=Missing, qux=Missing):
>         if baz is Missing:
>             baz = []
>         #code
> 
> or even:
> 
>     def foo(x, y, z, bar=, qux=):
>         if baz is Missing:
>             baz = []
>         #code

why not even

def foo(x, y, z, bar=..., qux=...):
    if bar is Ellipsis:
        # foo

;)

Georg