错误处理

错误处理

记录错误

---

python内置的logging模块可以非常容易的记录错误信息
程序打印完错误信息后会继续执行，并正常退出

import logging
def foo(s):
    return 10/int(s)

def bar(s):
    return foo(s)

def main():
    try:
        bar('0')
    except Exception as e:
        logging.exception(e)

main()
print('END')

ERROR:root:division by zero
Traceback (most recent call last):
  File "<ipython-input-2-769f334497f9>", line 10, in main
    bar('0')
  File "<ipython-input-2-769f334497f9>", line 6, in bar
    return foo(s)
  File "<ipython-input-2-769f334497f9>", line 3, in foo
    return 10/int(s)
ZeroDivisionError: division by zero


END

抛出错误

---

• 因为错误是class,捕获一个错误就是捕获到该类的一个实例。因此错误不是凭空产生的而是有意创建并抛出的。
• python的内置函数可以抛出很多类型的错误，同样我们也可以自己编写

class FooError(ValueError):
    pass

def foo(s):
    n = int(s)
    if n==0:
        raise FooError('invalid value: %s' %n)
    return 10/n

foo('0')

---------------------------------------------------------------------------

FooError                                  Traceback (most recent call last)

<ipython-input-7-c3d12b1e6433> in <module>()
      8     return 10/n
      9 
---> 10 foo('0')


<ipython-input-7-c3d12b1e6433> in foo(s)
      5     n = int(s)
      6     if n==0:
----> 7         raise FooError('invalid value: %s' %n)
      8     return 10/n
      9 


FooError: invalid value: 0

def foo(s):
    n = int(s)
#     if n == 0:
#         raise ValueError('invalid value: %s' %s)
    return 10/n

def bar():
    try:
        foo('0')
    except ZeroDivisionError as e:
        print('ValueError')
        raise

bar()

ValueError



---------------------------------------------------------------------------

ZeroDivisionError                         Traceback (most recent call last)

<ipython-input-7-739ddad24540> in <module>()
     12         raise
     13 
---> 14 bar()


<ipython-input-7-739ddad24540> in bar()
      7 def bar():
      8     try:
----> 9         foo('0')
     10     except ZeroDivisionError as e:
     11         print('ValueError')


<ipython-input-7-739ddad24540> in foo(s)
      3 #     if n == 0:
      4 #         raise ValueError('invalid value: %s' %s)
----> 5     return 10/n
      6 
      7 def bar():


ZeroDivisionError: division by zero

try:
    print('try...')
    r = 10 / 0
    print('result:', r)
except ZeroDivisionError as e:
    print('except:', e)
finally:
    print('finally...')
print('END')

try...
except: division by zero
finally...
END