为什么要编写异常代码?
如果不编写异常代码,当代码存在异常时会进行报错,无法继续执行代码;编写异常代码后,捕捉当异常后,可以跟据相应的代码进行错误提示,从而使程序继续执行下去
常见异常
Exception 常规错误的基类
AttributeError 对象没有这个属性
IOError 输入/输出操作失败
IndexError 序列中没有此索引(index)
KeyError 映射中没有这个键
NameError 未声明/初始化对象 (没有属性)
SyntaxError Python 语法错误
SystemError 一般的解释器系统错误
ValueError 传入无效的参数
SystemExit 解释器请求退出
BaseException 所有异常的基类
AssertionError 断言语句失败
ZeroDivisionError 除(或取模)零 (所有数据类型)
TypeError 对类型无效的操作
例1(try捕捉异常)
def exp_exception(x,y):
try:
a=x/y
print('a=',a)
return a
except Exception:
print('程序异常,被除数不能为0')
exp_exception(2,0)
>>>程序异常,被除数不能为0
例2:
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
b=name
except ZeroDivisionError:
print('this is ZeroDivisionError')
mult_exceotion(2,0)
>>> this is ZeroDivisionError
mult_exceotion(2,1)
>>> NameError: name 'name' is not defined
例3(多异常):
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
b=name
except (ZeroDivisionError,NameError,TypeError):
print('one of ZeroDivisionError or NameError or TypeError')
mult_exceotion(2,1)
>>> one of ZeroDivisionError or NameError or TypeError
例4(捕捉异常信息):
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
b=name
except (ZeroDivisionError,NameError,TypeError) as e:
print(e)
mult_exceotion(2,1)
>>> name 'name' is not defined
例5(无法判断是何种异常):
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
b=name
except :
print('Error happened')
mult_exceotion(2,'')
>>>Error happened
一般不建议用此方法,因为无法对异常进行判断,从而解决异常错误
例6(和else一起使用)
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
except (ZeroDivisionError,NameError,TypeError) as e:
print(e)
else:
print('it went as exception')
mult_exceotion(2,1)
>>> it went as exception
例7(自定义异常):
#-*-coding:utf-8-*-
class MyError(Exception):
def __init__(self):
pass
def __str__(self):
return 'this is self define error'
def my_error_test():
try:
raise MyError() #raise用来抛出异常
except MyError as e:
print('exception info:',e)
my_error_test()
>>> exception info: this is self define error
例8(finally):
#-*-coding:utf-8-*-
def mult_exceotion(x,y):
try:
a=x/y
except ZeroDivisionError as e:
print(e)
finally:
print('no matter what happened')
mult_exceotion(2,0)
>>>division by zero
>>>no matter what happened
