033异常处理：你不可能总是对的2
本帖最后由 人若有情死得早 于 2017-7-9 22:55 编辑1.try-except语句
try:
检测范围
except Exception:
出现异常（Exception）后的处理代码
1)代码：
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
Traceback (most recent call last):
File "C:\Users\Administrator\Desktop\test.py", line 1, in <module>
f = open('我为什么是一个文件.txt')
FileNotFoundError: No such file or directory: '我为什么是一个文件.txt'
2)使用try-except修改后:
try:
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError:
print('文件出错啦T_T')
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
文件出错啦T_T
3)加上as reason将程序检测到出错的信息输出
try:
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError as reason:
print('文件出错啦T_T\n错误的原因是:'+ str(reason))
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
文件出错啦T_T
错误的原因是: No such file or directory: '我为什么是一个文件.txt'
4)增加多个except语句，提取代码段不同的异常问题
try:
sum = 1 + '1'
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError as reason:
print('文件出错啦T_T\n错误的原因是:'+ str(reason))
except TypeError as reason:
print('类型出错啦T_T\n错误的原因是:'+ str(reason))
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
类型出错啦T_T
错误的原因是:unsupported operand type(s) for +: 'int' and 'str'
5)如果except中为包含程序中存在的异常时，程序会直接爆出异常
try:
int('abc')
sum = 1 + '1'
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except OSError as reason:
print('文件出错啦T_T\n错误的原因是:'+ str(reason))
except TypeError as reason:
print('类型出错啦T_T\n错误的原因是:'+ str(reason))
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
Traceback (most recent call last):
File "C:\Users\Administrator\Desktop\test.py", line 2, in <module>
int('abc')
ValueError: invalid literal for int() with base 10: 'abc'
或者：
try:
sum = 1 + '1'
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except (OSError, TypeError):
print('出错啦T_T')
>>>
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
出错啦T_T
6)通用程序检测异常，并且报出异常，但是不详细（不推荐）
try:
int('abc')
sum = 1 + '1'
f = open('我为什么是一个文件.txt')
print(f.read())
f.close()
except:
print('出错啦T_T')
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
出错啦T_T
2.try-finally
finally:
无论如何都会被执行的代码
try:
f = open('我为什么是一个文件.txt', 'w')
print(f.write('我存在了！'))
sum = 1 + '1'
except (OSError, TypeError):
print('出错啦T_T')
finally:
f.close()
============== RESTART: C:\Users\Administrator\Desktop\test.py ==============
5
出错啦T_T
3.raise语句
>>> raise
Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
raise
RuntimeError: No active exception to reraise
>>> 1 / 0
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
1 / 0
ZeroDivisionError: division by zero
>>> raise ZeroDivisionError
Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
raise ZeroDivisionError
ZeroDivisionError
>>> raise ZeroDivisionError('除数为零的异常')
Traceback (most recent call last):
File "<pyshell#3>", line 1, in <module>
raise ZeroDivisionError('除数为零的异常')
ZeroDivisionError: 除数为零的异常
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