[Python-ideas] checking for identity before comparing built-in objects

[Chris Angelico]

On Tue, Oct 9, 2012 at 7:19 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> But they stop doing that as soon as they hit an if statement.
> It seems to me that the behaviour chosen for NaN comparison
> could just as easily make things go wrong as make them go
> right. E.g.
>
>    while not (error < epsilon):
>       find_a_better_approximation()
>
> If error ever ends up being NaN, this will go into an
> infinite loop.

But if you know that that's a possibility, you simply code your
condition the other way:

while error > epsilon:
   find_a_better_approximation()

Which will then immediately terminate the loop if error bonks to NaN.

ChrisA