tags.py 文件源码

def eval_condition(self, condition):
        # exceptions are handled by the caller
        parser = BooleanParser(env, condition, state='variable')
        expr = parser.parse_expression()
        if not parser.stream.eos:
            raise ValueError('chunk after expression')

        def eval_node(node):
            if isinstance(node, nodes.CondExpr):
                if eval_node(node.test):
                    return eval_node(node.expr1)
                else:
                    return eval_node(node.expr2)
            elif isinstance(node, nodes.And):
                return eval_node(node.left) and eval_node(node.right)
            elif isinstance(node, nodes.Or):
                return eval_node(node.left) or eval_node(node.right)
            elif isinstance(node, nodes.Not):
                return not eval_node(node.node)
            elif isinstance(node, nodes.Name):
                return self.tags.get(node.name, False)
            else:
                raise ValueError('invalid node, check parsing')

        return eval_node(expr)