ROS中如何在另一Python文件中使用话题接收的变量？

你的问题核心有两点：

1. 另一个文件中创建的listenerPy实例从未启动ROS订阅逻辑，也没处理回调，导致received_integer始终是初始的None
2. ROS节点默认是独立进程，不同进程间无法直接共享内存变量，必须用ROS原生通信机制实现数据传递

下面分两种场景给出解决方法：

场景1：两个逻辑在同一个进程内运行 #

修改listener.py，将ROS的spin()放在后台线程运行，避免阻塞主线程：

#!/usr/bin/env python

import rospy
from std_msgs.msg import Int32
import threading

class listenerPy:

    def __init__(self):
        self.received_integer = None
        self._spin_thread = None

    def callback(self, data):       
        self.received_integer = data.data
        print(self.received_integer)     
        
    def start_listener(self):
        # 避免重复初始化节点
        if not rospy.is_initialized():
            rospy.init_node('listener', anonymous=True)        
        rospy.Subscriber('chatter', Int32, self.callback)
        # 用守护线程运行spin，不阻塞主线程
        self._spin_thread = threading.Thread(target=rospy.spin)
        self._spin_thread.daemon = True
        self._spin_thread.start()

    def stop_listener(self):
        if self._spin_thread and self._spin_thread.is_alive():
            rospy.signal_shutdown("Stopping listener")
            self._spin_thread.join()

if __name__ == '__main__':
    try:
        listener = listenerPy()
        listener.start_listener()
        rospy.spin()
    except rospy.ROSInterruptException:
        pass

另一个文件修改为：

#!/usr/bin/env python

from listener import listenerPy
from time import sleep
import rospy

def main():
    # 初始化ROS节点
    if not rospy.is_initialized():
        rospy.init_node('data_consumer', anonymous=True)
    
    local_var = listenerPy() 
    local_var.start_listener()  # 启动订阅逻辑
    
    try:
        while not rospy.is_shutdown():
            value = local_var.received_integer
            print(value)
            sleep(1)
    except KeyboardInterrupt:
        local_var.stop_listener()

if __name__ == '__main__':
    main()

场景2：两个独立ROS节点（分开运行两个脚本） #

这种场景下必须用ROS的通信机制传递数据，这里用参数服务器实现：

修改listener.py，将收到的数据写入参数服务器：

#!/usr/bin/env python

import rospy
from std_msgs.msg import Int32

class listenerPy:

    def __init__(self):
        self.received_integer = None

    def callback(self, data):       
        self.received_integer = data.data
        rospy.set_param('/received_integer', self.received_integer)  # 写入参数服务器
        print(self.received_integer)     
        
    def listener(self):
        rospy.init_node('listener', anonymous=True)        
        rospy.Subscriber('chatter', Int32, self.callback)
        rospy.spin()

if __name__ == '__main__':
    try:
        listener = listenerPy()
        listener.listener()
    except rospy.ROSInterruptException:
        pass

另一个文件从参数服务器读取数据：

#!/usr/bin/env python

import rospy
from time import sleep

def main():
    rospy.init_node('data_reader', anonymous=True)
    
    while not rospy.is_shutdown():
        try:
            value = rospy.get_param('/received_integer')
            print(value)
        except KeyError:
            print("暂无可用数据")
        sleep(1)

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        pass 

内容的提问来源于stack exchange，提问作者Bo Mengels