Python global lock using files

lock.py

from contextlib import contextmanager

class LockError(Exception): pass

@contextmanager
def lock(lock_filename, force_lock=False):
    forced = False

    lockerror = False
    try:
        if os.path.exists(lock_filename):
            if not force_lock:
                lockerror = True
                raise LockError('Already locked')
            forced = True
        else:
            with open(lock_filename, 'w') as f:
                f.write(':)')
        
        yield
    finally:
        if not forced and not lockerror:
            try:
                os.remove(lock_filename)
            except OSError:
                pass

usage.py

with lock('/tmp/something'):
    do_something()