[Python-Dev] Assigning to __debug__

[Martin v. Loewis]

> I checked in a fix to IDLE too, but it seems you were using an
> externally-installed version of IDLE.

Sorry about that, I used actually one from CVS: with a sticky 2.0 tag
:-(

> Assigning to __debug__ was never well-defined.  You used it at your
> own risk.

When __debug__ was first introduced, the NEWS entry read

# Without -O, the assert statement actually generates code that first
# checks __debug__; if this variable is false, the assertion is not
# checked.  __debug__ is a built-in variable whose value is
# initialized to track the -O flag (it's true iff -O is not
# specified).  With -O, no code is generated for assert statements,
# nor for code of the form ``if __debug__: <something>''.

So it clearly says that it is a variable, and that assert will check
its value at runtime. I can't quote any specific messages, but I
recall that you've explained it that way also in the public.

Regards,
Martin