If a flag wouldn't work, what about a pragma? Pragma smell a bit unpythonic to me, but we did have a pragma for source encoding and unicode literals in Python 2, so it's not unprecedented. How much would it solve efficiency-wise if you could just write at the top of a particular module ##ORIGINAL BUILTINS ONLY PLEASE ? Or is this the first step on the dark path to Perl 6?
Again, this would encourage people to put such junk in every module they write, so it would lose its value. At this point in the thread I am tempted to propose an optimization moratorium, just to stop the flood of poorly-thought-through proposals. If you really want to make Python faster, don't waste your time in this thread. Go contribute to PyPy or Unladen Swallow. Or go fix the GIL, so we can use multiple cores. -- --Guido van Rossum (python.org/~guido)