异常处理

错误:

1.语法错误

print(111

[1;2;3;4]

2.逻辑错误

lst = [1,2,3]

lst[5]

dic =

dic["name"]

print(a)

print(111

1 + "alex"

int("alex")

name = "alex"

def func():

print(name)

name = "a"

func()

什么异常?

除去语法错误的就是异常

异常划分的很细

常用,更多

异常处理:

处理异常:

1. if

num = input(">>")

if num.isdecimal():

int(num)

if len(num) == 0:

pass

if 处理一些简单的异常,if异常处理的方式

2. try

try: # 尝试

int("alex")

except ValueError:

"""其他代码逻辑"""

为什么要用异常处理?

1.出现异常,异常下方的代码就不执行了(中断了)

2.用户体验不良好

异常处理:

检测到异常后"跳"过异常及异常下发的代码

try:

[1,2,3][7]

print(111)

dic =

dic["name"]

except Exception:

pass

异常分支:

根据不同分支,执行不同逻辑

try:

int(input("请输入数字:"))

except ValueError as e:

print(e)

# print(34533)

int(input("请输入数字:"))

try:

int(input("请输入数字:"))

except Exception as e:

print(e)

int(input("请输入数字:"))

分支 + 万能 + else + finally

try:

num = int(input("请输入数字:"))

lst = [1,2,3]

# dic =

# print(dic[num])

print(lst[num])

except ValueError as e:

print(e)

except KeyError as e:

print(f"没有{e}这个键")

except IndexError as e:

print(e)

except Exception as e:

print(e)

else:

print("都没有错,走我!")

finally:

print("有错没有错,都走我!,清理工作")

class EvaException(BaseException):

def init(self,msg):

self.msg = msg

def str(self):

return self.msg

try:

a = EvaException('类型错误')

raise a

except EvaException as e:

print(e)

断言

assert 条件

assert 1 == 1

if 1 == 1:

print(111)

assert 1 == 2

if 1 == 2:

print(222)

分支 + 万能 + else + finally