True/False

[Ian Bicking]

On Tue, 2003-04-22 at 16:17, Erik Max Francis wrote:
> If done, then a blanket statement like yours above would start
> generating warnings eventually; they'd be harmless warnings, but they'd
> be unnerving and annoying.
> 
> > import sys
> > if sys.version_info < (2, 3):
> >     True, False = 1==1, 0==1
> 
> This would be okay (although the untyped version of the True and False
> builtins were introduced in 2.2, not 2.3).  The solution I've adopted
> is:
> 
> 	try:
> 	    True
> 	except NameError:
> 	    True, False = 1, 0

Not safe at all:

Python 2.3a2+ (#2, Mar 21 2003, 22:13:05) 
[GCC 3.2.3 20030316 (Debian prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> try:
...     None
... except NameError:
...     None = 0
... 
<stdin>:4: SyntaxWarning: assignment to None

Syntax-related errors/warnings aren't runtime.  Though strangely:

>>> if 0:
...     None = 0
... 
>>> if False:
...     None = 0
... 
<stdin>:2: SyntaxWarning: assignment to None


Maybe there's an optimization going on in this case, though (and to do
the optimization properly in both cases you'd have to catch assignment
to False too!)

  Ian