[Python-Dev] Assignment to None

[Tony Nelson]

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.

>>> f.None = 1
SyntaxError: assignment to None
>>> f.None
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'Foo' object has no attribute 'None'
>>> setattr(f, 'None', 1)
> f.None
1
>>>
-- 
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