###实验十：异常 ####一、实验目的：本实验我们知道了异常是什么，然后怎样处理异常以及抛出异常。记得在前面说过的 with 语句吧，它是 try-finally 块的简写，使用 with 语句能保证文件始终被关闭。 ####二、知识要点： +NameError +TypeError +异常处理（try..except） +异常抛出（raise） +finally 子句 ####三、实验内容 ####1、异常 ``` print("hello world") ``` ####2、Name Error ``` >>> print(kushal) Traceback (most recent call last): File "", line 1, in NameError: name 'kushal' is not defined ``` ####3、TypeError ``` >>> print(1 + "kushal") Traceback (most recent call last): File "", line 1, in TypeError: unsupported operand type(s) for +: 'int' and 'str' ``` ####4、处理异常 ``` try: statements to be inside try clause statement2 statement3 ... except ExceptionName: statements to evaluated in case of ExceptionName happens ``` ``` >>> def get_number(): ... "Returns a float number" ... number = float(input("Enter a float number: ")) ... return number ... >>> >>> while True: ... try: ... print(get_number()) ... except ValueError: ... print("You entered a wrong value.") ... Enter a float number: 45.0 45.0 Enter a float number: 24,0 You entered a wrong value. Enter a float number: Traceback (most recent call last): File "", line 3, in File "", line 3, in get_number KeyboardInterrupt ``` ``` >>> try: ... input() # 输入的时候按下 Ctrl + C 产生 KeyboardInterrupt ... except: ... print("Unknown Exception") ... Unknown Exception ``` ####5、抛出异常 ``` >>> raise ValueError("A value error happened.") Traceback (most recent call last): File "", line 1, in ValueError: A value error happened. ``` ``` >>> try: ... raise ValueError("A value error happened.") ... except ValueError: ... print("ValueError in our code.") ... ValueError in our code. ``` ####6、定义清理行为 ``` >>> try: ... raise KeyboardInterrupt ... finally: ... print('Goodbye, world!') ... Goodbye, world! KeyboardInterrupt Traceback (most recent call last): File "", line 2, in ? ``` ####四、运行结果 ____________________________________________________________________________________ ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1267874-20200306-1583455193213) ____________________________________________________________________________________

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