[Python-ideas] Make "is" checks on non-singleton literals errors

[Barry Warsaw]

On Oct 08, 2012, at 03:44 PM, Mike Graham wrote:

>I regularly see learners using "is" to check for string equality and
>sometimes other equality. Due to optimizations, they often come away
>thinking it worked for them.
>
>There are no cases where
>
>    if x is "foo":
>
>or
>
>   if x is 4:
>
>is actually the code someone intended to write.
>
>Although this has no benefit to anyone but new learners, it also
>doesn't really do any harm.

Conversely, I often see this:

    if x == None

and even

    if x == True

Okay, so maybe these are less harmful than the original complaint, but still,
yuck!

-Barry
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