Python异常处理

Question

C有perror和errno,它打印并存储遇到的最后一个错误.这在执行文件io时很方便,因为我不必将fstat()作为fopen()参数失败的每个文件向用户提供调用失败的原因.

我想知道在python中优雅地处理IOError异常时获取errno的正确方法是什么？

In [1]: fp = open("/notthere")
---------------------------------------------------------------------------
IOError                                   Traceback (most recent call last)

/home/mugen/ in ()

IOError: [Errno 2] No such file or directory: '/notthere'


In [2]: fp = open("test/testfile")
---------------------------------------------------------------------------
IOError                                   Traceback (most recent call last)

/home/mugen/ in ()

IOError: [Errno 13] Permission denied: 'test/testfile'


In [5]: try:
   ...:     fp = open("nothere")
   ...: except IOError:
   ...:     print "This failed for some reason..."
   ...:     
   ...:     
This failed for some reason...

Answer 1

Exception有一个errno属性:

try:
    fp = open("nothere")
except IOError as e:
    print(e.errno)
    print(e)

Answer 2

这是你如何做到的.另请参阅某些实用程序的errno模块和os.strerror功能.

import os, errno

try:
    f = open('asdfasdf', 'r')
except IOError as ioex:
    print 'errno:', ioex.errno
    print 'err code:', errno.errorcode[ioex.errno]
    print 'err message:', os.strerror(ioex.errno)

• http://docs.python.org/library/errno.html
• http://docs.python.org/library/os.html

有关IOError属性的更多信息,请参阅基类EnvironmentError:

• http://docs.python.org/library/exceptions.html?highlight=ioerror#exceptions.EnvironmentError

Answer 3

try:
    fp = open("nothere")
except IOError as err:
    print err.errno 
    print err.strerror