Question

我正在制作一个通过覆盆子Pi控制2台电机的程序。我正在运行python代码，我想知道如何实现以下目标：

运行motor1
同时运行motor2
等待两个电机完成
运行motor1
同时运行motor2

等

到目前为止，我所做的是创建一个Thread并使用队列。

class Stepper(Thread):

    def __init__(self, stepper):
        Thread.__init__(self)
        self.stepper = stepper    
        self.q = Queue(maxsize=0)

    def setPosition(self, pos):
        self.q.put(pos)

    def run(self):
        while not self.q.empty():
            item = self.q.get()
            // run motor and do some stuff 

thread_1 = Stepper(myStepper1)
thread_2 = Stepper(myStepper2)
thread_1.start()
thread_2.start()

loop = 10
while(loop):
    thread_1.setPosition(10)
    thread_2.setPosition(30)
    # I want to wait here
    thread_1.setPosition(10)
    thread_2.setPosition(30)
    loop = loop - 1

    thread_1.join()
    thread_2.join()

thread_1和thread_2都不会同时完成，具体取决于电机需要处理的步数。我曾尝试使用Lock（）功能，但我不确定如何正确实现它。我还想过重新创建线程，但不确定这是否是正确的解决方案。

Answer 1

您实际可以使用Semaphore：

from threading import Semaphore

class Stepper(Thread):

    def __init__(self, stepper, semaphore):
        Thread.__init__(self)
        self.stepper = stepper
        self.semaphore = semaphore

    def setPosition(self, pos):
        self.q.put(pos)

    def run(self):
        while not self.q.empty():
            try:
                # run motor and do some stuff
            finally:
                self.semaphore.release()  # release semaphore when finished one cycle

semaphore = Semaphore(2)
thread_1 = Stepper(myStepper1, semaphore)
thread_2 = Stepper(myStepper2, semaphore)
thread_1.start()
thread_2.start()

loop = 10
for i in range(loop):
    semaphore.acquire()
    semaphore.acquire()
    thread_1.setPosition(10)
    thread_2.setPosition(30)
    semaphore.acquire()
    semaphore.acquire()  # wait until the 2 threads both released the semaphore
    thread_1.setPosition(10)
    thread_2.setPosition(30)

Answer 2

您可以使用线程的join方法，如下所示：

thread_1.join() # Wait for thread_1 to finish
thread_2.join() # Same for thread_2

根据https://docs.python.org/3/library/threading.html#threading.Thread.join的文档：

线程可以多次join()。

要重复运行线程，您需要在每次运行后重新初始化Thread对象。

等待线程完成后再运行它们

2 个答案: