import mimetypes
import threading
import time

old_init = mimetypes.init

def work():
    print (mimetypes.guess_type("hglogo.png"))

def main():
    threads = []
    for i in range(20):
        threads.append(threading.Thread(target=work))
    for t in threads:
        t.start()
    for t in threads:
        t.join()

main()