Answer by m.wasowski for Get full path of currently open files

This seems to work (on Linux):

import subprocess
import shlex

cmd = shlex.split('lsof -F n +d .')
try:
    output = subprocess.check_output(cmd).splitlines()
except subprocess.CalledProcessError as err:
    output = err.output.splitlines()
output = [line[3:] for line in output if line.startswith('n./')]

# Out[3]: ['file.tmp']

it reads open files from current directory, non-recursively.

For recursive search, use +D option. Keep in mind, that it is vulnerable to race condition - when you get your ouput, situation might have changed already. It is always best to try to do something (open file), and check for failure, e.g. open file and catch exception or check for null FILE value in C.