def is_none_p(value): """Return True if value is None""" return value is None @retry(retry=(retry_if_result(is_none_p) | retry_if_exception_type())) def might_return_none(): print("返回 None 则重试") 也可以通过引发 TryAgain 异常随时显式重试: @retry def do_something(): resul...
1.2.5:if语句小结 if 后表达式返回值为True则执行其子代码块,然后此if语句到此终结,否则进入下一分支判断,直到满足其中一个分支,执行后终结if expression可以引入运算符:not,and,or,is,is not 多重expression为加强可读性最好用括号包含 if与else缩进级别一致表示是一对 elif与else都是可选的 一个if判断最多...
Please try again." super().__init__(self.message) def send_email(to, subject, body): if "@" not in to: raise InvalidEmailException(to) # 抛出异常 print(f"Email sent to {to} with subject '{subject}' and body '{body}'.") # 测试 try: send_email("invalid-email", "Test email...
raise 抛出的异常必须是一个异常实例或类(派生自 Exception 的类)。 四、清理动作(finally) try 语句有另一种可选的finally从句,用于自定义一些扫尾清理的工作。 try: x = int(input('please input an integer:')) if x > 5: print('Hello World!') except ValueError: print('It was not a number. ...
Exceptionis as a sort of structured "super go to". 异常是一种结构化的"超级goto". 作为一个数十年如一日地钟爱C语言的程序员(因为C程序员需要记忆的关键字很少,而且可以很惬意地玩内存),对于高级语言如Python里的异常(Exception)一直不甚理解,尤其是其实现机理。但读了《Learning Python》一书中上面这句...
while 1: try: n = int(input("enter a integer (0-exit): ")) print(n) if n == 0: break except: print("try again...") ''' enter a integer (0-exit): 5 5 enter a integer (0-exit): a try again... enter a integer (0-exit): 0 0 ''' 示例一。 用实例调用方法 calc(...
When an exception has been assigned using as target, it is cleared at the end of the except clause. This is as if except E as N: foo was translated into except E as N: try: foo finally: del N This means the exception must be assigned to a different name to be able to refer to...
处理程序只处理相应的 try 子句中发生的异常,而不处理同一 try 语句内其他处理程序中的异常。 一个 except 子句可以将多个异常命名为带括号的元组,例如: except (RuntimeError, TypeError, NameError): pass 1. 2. 如果发生的异常和 except 子句中的类是同一个类或者是它的基类,则异常和 except 子句中的类...
except Exception,e: print e else: break 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 以上代码执行过程: 首先执行内层的try,如果触发异常,捕获内层异常,打印信息“try again” 接着执行代码1/0,抛出异常,此异常抛给上层的try,然后被上层try对应的except捕获并打印异常信息;如果都没有异常发生,跳出循环 ...
However, if you have a more complex program, then you may want to handle errors more gracefully. For instance, you may need to call many processes over a long period of time. For this, you can use the try… except construct.An Example of Exception Handling Here’s a code snippet that...