[FRPythoneers] Python documentation and default expression
Mike.Olson at fourthought.com
Sun Mar 17 08:02:33 MST 2002
On Fri, 2002-03-15 at 15:28, Rob Riggs wrote:
> Mike Olson wrote:
> As I've just discovered. I think I will be much more careful about this
> in the future.
> If it doesn't do so already, this sounds like it could be a valuable
> test in PyChecker.
I don't think it does. I'm not sure if it could. How does it know what
> >also, if your counting clock cycles,
> >if foo is not None:
> >will actually be quicker.
> I've almost always used "if foo != None:". Is there a reason not to
> write it as such?
"is" is an identity check. At the C level, it compares pointer values
(one clock cycle). When you use "=", which is equality, it has to go
through (possiblly) all of the coercion routines, look for __cmp__ etc
so it will be slower.
For most applications it doesn't matter. I never ran into it until I
worked on optimizating of our Xslt processor. There, we were hitting if
statements 10,000 times and then we would see large differences.
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