Bug? Feature? setattr(foo, '3', 4) works!

[Cem Karan]

I'm bringing this discussion over from the python-ideas mailing list to see what people think. I accidentally discovered that the following works, at least in Python 3.4.2:

>>> class foo(object):
...     pass
... 
>>> setattr(foo, '3', 4)
>>> dir(foo)
['3', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
>>> getattr(foo, '3')
4
>>> bar = foo()
>>> dir(bar)
['3', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
>>> getattr(bar, '3')
4
>>> hasattr(foo, '3')
True
>>> hasattr(bar, '3')
True

However, the following doesn't work:

>>> foo.3
 File "<stdin>", line 1
   foo.3
       ^
SyntaxError: invalid syntax
>>> bar.3
 File "<stdin>", line 1
   bar.3
       ^
SyntaxError: invalid syntax

I'd like to suggest that getattr(), setattr(), and hasattr() all be modified so that syntactically invalid statements raise SyntaxErrors. In messages on python-ideas, Nick Coghlan mentioned that since a Namespace is just a dictionary, the normal error raised would be TypeError and not SyntaxError; I'd like to suggest special-casing this so that using getattr(), setattr(), and hasattr() in this way raise SyntaxError instead as I think that will be less astonishing.  

Thoughts?

Thanks,
Cem Karan