Python Basic Doubt

[Steven D'Aprano]

On Sat, 10 Aug 2013 20:21:46 -0700, Gary Herron wrote:

> Our knee-jerk reaction to beginners using "is" should be:
>      Don't do that!  You almost certainly want "==".   Consider "is" an
> advanced topic.
> 
> Then you can spend as much time as you want trying to coach them into an
> understanding of the precise details.  But until they have that
> understanding, they are well served by a rule-of-thumb that says:
>      Use "==" not "is" for comparisons.

"...except for comparing to None, where 99.99% of the time you do 
actually want an identity comparison."

This can lead into a more detailed explanation for why you should choose 
one over the other, or the incurious newbie could take it is something to 
be learned by rote. I have no problem with telling newbies that there is 
a reason for this apparently arbitrary rule, but they don't need to learn 
it *right now* if they don't want.

In any case, the rule can include "When in doubt, use equals". I'm good 
with that :-)


-- 
Steven