use fcntl.flock to ensure only one instance of a python script is running

import fcntl
from os import remove
from os.path import splitext
from time import sleep
def ():
    lock_file = '{}.lock'.format(splitext(__file__)[0])
    with open(lock_file, 'w') as lock_fp:
        try:
            fcntl.flock(lock_fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except IOError:
            print('Script has been running.')
            return
        else:
            print('Script starts to run.')
            sleep(10)
            print('Done!')
    remove(lock_file)
if __name__ == '__main__':
    main()