[Python-Dev] Assignment to None

[Thomas Lee]

Tony Nelson wrote:
> At 4:46 PM +0100 6/9/08, Michael Foord wrote:
>   
>> Alex Martelli wrote:
>>     
>>> The problem is more general: what if a member  (of some external
>>> object we're proxying one way or another) is named print (in Python <
>>> 3), or class, or...?  To allow foo.print or bar.class would require
>>> pretty big changes to Python's parser -- I have vague memories that
>>> the issue was discussed ages ago (possibly in conjunction with some
>>> early release of Jython) but never went anywhere much (including
>>> proposals to automatically append an underscore to such IDs in the
>>> proxying layer, etc etc).  Maybe None in particular is enough of a
>>> special case (if it just happens to be hugely often used in dotNET
>>> libraries)?
>>>
>>>       
>> 'None' as a member does occur particularly frequently in the .NET world.
>>
>> A halfway house might be to state (something like):
>>
>>    Python as a language disallows you from having names the same as
>> keywords or 'None'. An implementation restriction specific to CPython is
>> that the same restriction also applies to member names. Alternative
>> implementations are free to not implement this restriction, with the
>> caveat that code using reserved member names directly will be invalid
>> syntax for CPython.
>>     
>  ...
>
> Or perhaps CPython should just stop trying to detect this at compile time.
> Note that while assignment to ".None" is not allowed, setattr(foo, "None",
> 1) then referencing ".None" is allowed.
>
>   
I'm +0 on this at the moment, but I can understand the desire for it. 
Maybe we should stop trying to check for this assignment on attributes?

Currently there are separate checks for assignment to None: one for the 
"foo.None = ..." form, another for the "None = ..." form. Removing the 
check for the former looks like it would be a one-liner.

Cheers,
T