stack_context.py 文件源码

def __exit__(self, type, value, traceback):
        try:
            self.exit(type, value, traceback)
        finally:
            final_contexts = _state.contexts
            _state.contexts = self.old_contexts

            # Generator coroutines and with-statements with non-local
            # effects interact badly.  Check here for signs of
            # the stack getting out of sync.
            # Note that this check comes after restoring _state.context
            # so that if it fails things are left in a (relatively)
            # consistent state.
            if final_contexts is not self.new_contexts:
                raise StackContextInconsistentError(
                    'stack_context inconsistency (may be caused by yield '
                    'within a "with StackContext" block)')

            # Break up a reference to itself to allow for faster GC on CPython.
            self.new_contexts = None