how to find the owner of a file or directory in python

You want to use os.stat():

os.stat(path)
 Perform the equivalent of a stat() system call on the given path. 
 (This function follows symlinks; to stat a symlink use lstat().)

The return value is an object whose attributes correspond to the 
members of the stat structure, namely:

- st_mode - protection bits,
- st_ino - inode number,
- st_dev - device,
- st_nlink - number of hard links,
- st_uid - user id of owner,
- st_gid - group id of owner,
- st_size - size of file, in bytes,
- st_atime - time of most recent access,
- st_mtime - time of most recent content modification,
- st_ctime - platform dependent; time of most recent metadata 
             change on Unix, or the time of creation on Windows)

Example of usage to get owner UID:

from os import stat
stat(my_filename).st_uid

Note, however, that stat returns user id number (for example, 0 for root), not actual user name.

It's an old question, but for those who are looking for a simpler solution with Python 3.

You can also use Path from pathlib to solve this problem, by calling the Path's owner and group method like this:

from pathlib import Path

path = Path("/path/to/your/file")
owner = path.owner()
group = path.group()
print(f"{path.name} is owned by {owner}:{group}")

So in this case, the method could be the following:

from typing import Union
from pathlib import Path

def find_owner(path: Union[str, Path]) -> str:
    path = Path(path)
    return f"{path.owner()}:{path.group()}"

I'm not really much of a python guy, but I was able to whip this up:

from os import stat
from pwd import getpwuid

def find_owner(filename):
    return getpwuid(stat(filename).st_uid).pw_name

I stumbled across this recently, looking to get owner user and group information, so I thought I'd share what I came up with:

import os
from pwd import getpwuid
from grp import getgrgid

def get_file_ownership(filename):
    return (
        getpwuid(os.stat(filename).st_uid).pw_name,
        getgrgid(os.stat(filename).st_gid).gr_name
    )