Python异常处理

Question

C有perror和errno，它会打印并存储遇到的最后一个错误。这在做文件io时很方便，因为我不必为每个失败的文件fstat（）作为fopen（）的参数来向用户展示调用失败的原因。

我想知道在python中正常处理IOError异常时抓取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

例外有一个errno属性：

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

Answer 2

这里是你如何能做到这一点。另请参阅errno模块和os.strerror函数的某些实用程序。

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

有关的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