Python线程。看不到当前状态

Question

我有4个线程，我想看看它们是否还活着并已正确启动。 is_alive()不返回任何内容，但是在我的日志文件中看到该进程正在运行。

    def session_start()
       while True:
           # here I poll my database and send request and 
           # store response result back to database

    def main():
        session_start_thread = Thread(app.session_start())
        print('Starting thread 1...')
        session_start_thread.start()
        if session_start_thread.is_alive():
            print('Thread 1 is runnning')
        else:
            print("Thread 1 wasn't started")