Access to errno from Python?

Question

I am stuck with a fairly complex Python module that does not return useful error codes (it actually fails disturbingly silently). However, the underlying C library it calls

Answer 1

Here is a snippet of code that allows to access errno:

from ctypes import *

libc = CDLL("libc.so.6")

get_errno_loc = libc.__errno_location
get_errno_loc.restype = POINTER(c_int)

def errcheck(ret, func, args):
    if ret == -1:
        e = get_errno_loc()[0]
        raise OSError(e)
    return ret

copen = libc.open
copen.errcheck = errcheck

print copen("nosuchfile", 0)

The important thing is that you check errno as soon as possible after your function call, otherwise it may already be overwritten.