Untested readwritelock for Python threading

readwritelock.py

class ReadWriteLock:
    def __init__(self):
        self.readers = 0
        self.lock = threading.Condition(threading.Lock())

    @contextmanager
    def lock_for_reading(self):
        self.lock.acquire()
        try:
            self.readers += 1
        finally:
            self.lock.release()

        try:
            yield
        finally:
            self.lock.acquire()
            try:
                self.readers -= 1
            finally:
                self.lock.release()

    @contextmanager
    def lock_for_writing(self):
        self.lock.acquire()
        self.lock.wait_for(lambda: self.readers == 0)
        try:
            yield
        finally:
            self.lock.release()