parser.py 文件源码

def parse_from(self):
        node = nodes.FromImport(lineno=next(self.stream).lineno)
        node.template = self.parse_expression()
        self.stream.expect('name:import')
        node.names = []

        def parse_context():
            if self.stream.current.value in ('with', 'without') and \
               self.stream.look().test('name:context'):
                node.with_context = next(self.stream).value == 'with'
                self.stream.skip()
                return True
            return False

        while 1:
            if node.names:
                self.stream.expect('comma')
            if self.stream.current.type == 'name':
                if parse_context():
                    break
                target = self.parse_assign_target(name_only=True)
                if target.name.startswith('_'):
                    self.fail('names starting with an underline can not '
                              'be imported', target.lineno,
                              exc=TemplateAssertionError)
                if self.stream.skip_if('name:as'):
                    alias = self.parse_assign_target(name_only=True)
                    node.names.append((target.name, alias.name))
                else:
                    node.names.append(target.name)
                if parse_context() or self.stream.current.type != 'comma':
                    break
            else:
                break
        if not hasattr(node, 'with_context'):
            node.with_context = False
            self.stream.skip_if('comma')
        return node