Message10449

Artem, I'm very glad you could conduct that test! This is very helpful.

Using `is` to compare against singletons is a standard example of when identity comparisons are appropriate in Python (or other languages). But as we see, sre_constants.AT, etc, are not singletons when we consider module reloading.

The minor possible speedup of comparing references in regular expression compilation instead of values is a good example of premature optimization.

I'm not certain about being able to backport 2.7.x changes to 2.5.x There is an stalled release candidate process for 2.5.4 that has been that way for a number of years. It is possible that this bug might be worth fixing in 2.5.4 because of its simplicity: we know that value equality should always work in this compilation; and now we know that identity comparison does not. Also I don't believe there has been any changes in this particular code since 2.5. And by fixing this bug, we might get over the hump of getting 2.5.4 really out.