Python异常处理详解-优快云博客

本文详细介绍了Python中的异常处理机制，包括基本的try-except结构，如何捕获已知异常、所有异常以及处理多个异常。此外，还讲解了try-except-else、try-except-finally和try-except-else-finally的使用场景，并提供了自定义异常的示例。

1.抓取已知异常：

try:
    a
except NameError as e:
    print("catch Error:",e)

2.捕获所有异常：

try:
    a
except:
    print("catch Error")

3.处理多个异常：

try:
    f=open('1.txt')
    line=f.read(2)
    num=int(line)
    print(num)
except IOError as e:
    print("catch IOError:",e)
except ValueError as e:
    print("catch ValueError:",e)

4.try-except-else：

try:
    f=open('1.txt','w')
    line=f.write('2')
except IOError as e:
    print("catch IOError:",e)
except ValueError as e:
    print("catch ValueError:",e)
else:
    print("no exception")

5.try-except-finally：

try:
    f=open('1.txt','w')
    line=f.write('2')
except IOError as e:
    print("catch IOError:",e)
except ValueError as e:
    print("catch ValueError:",e)
finally:
    f.close()
    print("always do")

6.try-except-else-finally：

try:
    f=open('1.txt','w')
    line=f.write('2')
except IOError as e:
    print("catch IOError:",e)
except ValueError as e:
    print("catch ValueError:",e)
else:
    print("no exception")
finally:
    f.close()
    print("always do")

7.自定义异常：

class CustomError(Exception):
    def __init__(self,info):
        Exception.__init__(self)
        self.errorinfo=info
    def __str__(self):
        return "Custom:%s" % self.errorinfo
try:
    raise CustomError("test failed")
except CustomError as e:
    print("exception:",e)

python异常