How to get the errno of an IOError?

Question

C has perror and errno, which print and store the last error encountered. This is convenient when doing file io as I do not have to fstat() every file that fails as an argument to fopen() to present the user with a reason why the call failed.

I was wondering what is the proper way to grab errno when gracefully handling the IOError exception in python?

 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

The Exception has an errno attribute:

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

Answer 2

Here's how you can do it. Also see the errno module and os.strerror function for some utilities.

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

For more information on IOError attributes, see the base class EnvironmentError:

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