Martin v. Löwis wrote:
The question is, what is the specification for Python.
Now, that's a more interesting question than the question originally
asked (which I interpreted as "why does it work the way it works").
The only indication in the specification of that feature I could find
was:
http://docs.python.org/dev/library/constants.html
"Changed in version 2.4: Assignments to None are illegal and raise a
SyntaxError."
Now, given that this talks about the built-in namespace, this *doesn't*
specify that foo.None=1 should also raise a syntax error.
So the implementation apparently deviates from the specification.
In Python 3, None, True, and False are keywords, so clearly, the
intended semantics is also the implemented one (and the language
description for 2.x needs to be updated/clarified).
Interestingly enough, the semantics of True, False and None are
different from one another in 2.6:
True = "blah" and False = 6 are perfectly legal in Python <=2.6.
Funny, I just ran into this. I was trying to figure out why the AST
optimization code was breaking test_xmlrpc ... turns out xmlrpclib
defines xmlrpclib.True and xmlrpclib.False and the optimizer was trying
to resolve them as constants while compiling the module. Ouch.
What happened in 3k? Were the constants in xmlrpclib renamed/removed?
Cheers,
T
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