If 0. Etc. are also compiled out, at compile time __debug__ is simply False or True and the existing optimization paths take care of it.
Assigning to __debug__ wouldn't do anything to the compiler as it never actually reads the variable, so assignment would just cause weirdness from other use
Assigning to __debug__ wouldn't do anything to the compiler as it never actually reads the variable, so assignment would just cause weirdness from other use