File locking

[Dr. Who]

I'm always disappointed when I find something that Python doesn't
handle in a platform independent way.  It seems to me that file
locking is in that boat.

1. I don't see a way to atomically open a file for writing if and only
if it doesn't exist without resorting to os.open and specialized
platform O_XXX flags.

2. I don't see a way to atomically open a file for writing and obtain
a lock on the file.

3. I don't see a platform independent way to obtain a lock on a file.
You have to do something goofy like
if sys.platform == win32:
    import msvcrt
else:
    import fcntl
and then similar things to call the correct functions with the correct
flags.

Please let me know if I'm missing something since they seem like
normal file operations that I would hope Python would abstract away.
If not, are there any PEPs concerning this for Python3K?

Thanks,
Jeff