Error with os.open in Python

I'm trying to create and write a file if it does not exist yet, so that it is co-operatively safe from race conditions, and I'm having (probably stupid) problem. First, here's code: ``` import os def safewrite(text, filename): print "Going to open", filename fd = os.open(filename, os.O_CREAT | os.O_EXCL, 0666) ##### problem line? print "Going to write after opening fd", fd os.write(fd, text) print "Going to close after writing", text os.close(fd) print "Going to return after closing" #test code to verify file writing works otherwise f = open("foo2.txt", "w") f.write("foo\n"); f.close() f = open("foo2.txt", "r") print "First write contents:", f.read() f.close() os.remove("foo2.txt") #call the problem method safewrite ("test\n", "foo2.txt") ``` Then the problem, I get exception: ``` First write contents: foo Going to open foo2.txt Going to write after opening fd 5 Traceback (most recent call last): File "/home/user/test.py", line 21, in <module> safewrite ("test\n", "foo2.txt") File "/home/user/test.py", line 7, in safewrite os.write(fd, text) OSError: [Errno 9] Bad file descriptor ``` Probable problem line is marked in the code above (I mean, what else could it be?), but I can't figure out how to fix it. What is the problem? Note: above was tested in a Linux VM, with Python 2.7.3. If you try the code and it works for you, please write a comment with your environment. Alternative code to do the same thing at least as safely is also very welcome.