ros2与Python入门教程-使用消息

**ros2与Python入门教程-使用消息 **

说明：

• 介绍如何python来测试消息

步骤：

• 如何创建消息 ，参考ROS2与C++入门教程-创建消息（msg）文件
• 利用python来测试消息
• 使用之前建立的py_pubsub包
• 新建文件

cd ~/dev_ws/src/py_pubsub/py_pubsub
vim  publisher_member_function_num.py

• 内容如下

import rclpy
from rclpy.node import Node

from tutorial_interfaces.msg import Num    # CHANGE


class MinimalPublisher(Node):

    def __init__(self):
        super().__init__('minimal_publisher')
        self.publisher_ = self.create_publisher(Num, 'topic', 10)     # CHANGE
        timer_period = 0.5
        self.timer = self.create_timer(timer_period, self.timer_callback)
        self.i = 0

    def timer_callback(self):
        msg = Num()                                           # CHANGE
        msg.num = self.i                                      # CHANGE
        self.publisher_.publish(msg)
        self.get_logger().info('Publishing: "%d"' % msg.num)  # CHANGE
        self.i += 1


def main(args=None):
    rclpy.init(args=args)

    minimal_publisher = MinimalPublisher()

    rclpy.spin(minimal_publisher)

    minimal_publisher.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()

• 新建文件

cd ~/dev_ws/src/py_pubsub/py_pubsub
vim subscriber_member_function_num.py

• 内容如下：

import rclpy
from rclpy.node import Node

from tutorial_interfaces.msg import Num        # CHANGE


class MinimalSubscriber(Node):

    def __init__(self):
        super().__init__('minimal_subscriber')
        self.subscription = self.create_subscription(
            Num,                                              # CHANGE
            'topic',
            self.listener_callback,
            10)
        self.subscription

    def listener_callback(self, msg):
            self.get_logger().info('I heard: "%d"' % msg.num) # CHANGE


def main(args=None):
    rclpy.init(args=args)

    minimal_subscriber = MinimalSubscriber()

    rclpy.spin(minimal_subscriber)

    minimal_subscriber.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()

• 变更package.xml，增加

<exec_depend>tutorial_interfaces</exec_depend>

• 变更setup.py,增加入口

entry_points={
        'console_scripts': [
                'talker_num = py_pubsub.publisher_member_function_num:main',
                'listener_num = py_pubsub.subscriber_member_function_num:main',
        ],
},

• 安装依赖

rosdep install -i --from-path src --rosdistro foxy -y

• 编译

colcon build --packages-select py_pubsub

• 新开终端，运行

. install/setup.bash
ros2 run py_pubsub talker_num

• 新开终端，运行

. install/setup.bash
ros2 run py_pubsub listener_num