Function cb

Lib/importlib/_bootstrap.py:448–457

(ref, name=name)

                lock = _ModuleLock(name)

            def cb(ref, name=name):
                _imp.acquire_lock()
                try:
                    # bpo-31070: Check if another thread created a new lock
                    # after the previous lock was destroyed
                    # but before the weakref callback was called.
                    if _module_locks.get(name) is ref:
                        del _module_locks[name]
                finally:
                    _imp.release_lock()

            _module_locks[name] = _weakref.ref(lock, cb)
    finally: