There is another one which is trickier to find: [__builtin__.__builtins__ == __builtin__]

Would something like: [do not add builtins to builtin work?

No, because there is another one that is even trickier to find :-)

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print r <rexec.RExec instance at 0x81f7cac> print r.modules['__builtin__'].open.im_self <rexec.RExec instance at 0x81f7cac>

Please see my other message; I think modules should be gc'ed. Regards, Martin