New submission from Nick Coghlan <ncogh...@gmail.com>:
While trying to create an example for a pickle bug discussion, I deliberately dropped `__main__` out of sys.modules, and the REPL session lost all of its runtime state. Simplified reproducer: ``` >>> import sys >>> mod = sys.modules[__name__] >>> sys.modules[__name__] = object() >>> dir() Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'dir' is not defined ``` (Initially encountered on Python 2.7, reproduced on Python 3.7) If I'd just dropped the reference to `__main__` entirely, that would make sense (since modules clear their namespaces when they go away), but I didn't: I saved a reference in a local variable first. So it appears the CPython REPL isn't keeping a strong reference to either `__main__` or `__main__.__dict__` between statements, so the cyclic GC kicked in and decided the module could be destroyed. ---------- messages: 340516 nosy: ncoghlan priority: normal severity: normal stage: test needed status: open title: Dropping __main__ from sys.modules clears the REPL namespace type: behavior versions: Python 2.7, Python 3.7, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue36665> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
