checker.py 文件源码

def EXCEPTHANDLER(self, node):
        if PY2 or node.name is None:
            self.handleChildren(node)
            return

        # 3.x: the name of the exception, which is not a Name node, but
        # a simple string, creates a local that is only bound within the scope
        # of the except: block.

        for scope in self.scopeStack[::-1]:
            if node.name in scope:
                is_name_previously_defined = True
                break
        else:
            is_name_previously_defined = False

        self.handleNodeStore(node)
        self.handleChildren(node)
        if not is_name_previously_defined:
            # See discussion on https://github.com/PyCQA/pyflakes/pull/59

            # We're removing the local name since it's being unbound
            # after leaving the except: block and it's always unbound
            # if the except: block is never entered. This will cause an
            # "undefined name" error raised if the checked code tries to
            # use the name afterwards.
            #
            # Unless it's been removed already. Then do nothing.

            try:
                del self.scope[node.name]
            except KeyError:
                pass