IMHO, I don't think that MAXREPEAT should be defined in sre_constants.py _and_ SRE_MAXREPEAT defined in sre_constants.h. (In the latter case, why is it in decimal?)

I think that it should be defined in one place, namely sre_constants.h, perhaps as:

#define SRE_MAXREPEAT ~(SRE_CODE)0

and then imported into sre_constants.py.

That'll reduce the chance of an inadvertent mismatch, and it's the C code that's imposing the limit to the number of repeats, not the Python code.