ros2与Python入门教程-创建发布和订阅

来源:https://www.ncnynl.com/archives/202008/3818.html

说明：

介绍如何创建发布和订阅
步骤：

新建包

cd ~/dev_ws/src
ros2 pkg create --build-type ament_python py_pubsub
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在目录dev_ws/src/py_pubsub/py_pubsub下
新建文件publisher_member_function.py
内容如下：

import rclpy
from rclpy.node import Node

from std_msgs.msg import String


class MinimalPublisher(Node):

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

    def timer_callback(self):
        msg = String()
        msg.data = 'Hello World: %d' % self.i
        self.publisher_.publish(msg)
        self.get_logger().info('Publishing: "%s"' % msg.data)
        self.i += 1


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

    minimal_publisher = MinimalPublisher()

    rclpy.spin(minimal_publisher)

    # Destroy the node explicitly
    # (optional - otherwise it will be done automatically
    # when the garbage collector destroys the node object)
    minimal_publisher.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()
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更改package.xml
更改description，maintainer ，license相关和增加依赖

<description>Examples of minimal publisher/subscriber using rclpy</description>
<maintainer email="you@email.com">Your Name</maintainer>
<license>Apache License 2.0</license>

<exec_depend>rclpy</exec_depend>
<exec_depend>std_msgs</exec_depend>
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更改setup.py
与package.xml的内容匹配

maintainer='YourName',
maintainer_email='you@email.com',
description='Examples of minimal publisher/subscriber using rclpy',
license='Apache License 2.0',
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更改console_scripts内容如下：

entry_points={
        'console_scripts': [
                'talker = py_pubsub.publisher_member_function:main',
        ],
},
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在目录dev_ws/src/py_pubsub/py_pubsub下
新建文件subscriber_member_function.py
内容如下：

import rclpy
from rclpy.node import Node

from std_msgs.msg import String


class MinimalSubscriber(Node):

    def __init__(self):
        super().__init__('minimal_subscriber')
        self.subscription = self.create_subscription(
            String,
            'topic',
            self.listener_callback,
            10)
        self.subscription  # prevent unused variable warning

    def listener_callback(self, msg):
        self.get_logger().info('I heard: "%s"' % msg.data)


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

    minimal_subscriber = MinimalSubscriber()

    rclpy.spin(minimal_subscriber)

    # Destroy the node explicitly
    # (optional - otherwise it will be done automatically
    # when the garbage collector destroys the node object)
    minimal_subscriber.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()
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更改setup.py,增加入口

entry_points={
        'console_scripts': [
                'talker = py_pubsub.publisher_member_function:main',
                'listener = py_pubsub.subscriber_member_function:main',
        ],
},
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安装依赖

cd ~/dev_ws/
rosdep install -i --from-path src --rosdistro foxy -y
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编译

colcon build --packages-select py_pubsub
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新开终端，运行发布

. install/setup.bash
ros2 run py_pubsub talker
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效果如下：

[INFO] [minimal_publisher]: Publishing: "Hello World: 0"
[INFO] [minimal_publisher]: Publishing: "Hello World: 1"
[INFO] [minimal_publisher]: Publishing: "Hello World: 2"
[INFO] [minimal_publisher]: Publishing: "Hello World: 3"
[INFO] [minimal_publisher]: Publishing: "Hello World: 4"
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新开终端，运行订阅

. install/setup.bash
ros2 run py_pubsub listener
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效果如下：

[INFO] [minimal_subscriber]: I heard: "Hello World: 10"
[INFO] [minimal_subscriber]: I heard: "Hello World: 11"
[INFO] [minimal_subscriber]: I heard: "Hello World: 12"
[INFO] [minimal_subscriber]: I heard: "Hello World: 13"
[INFO] [minimal_subscriber]: I heard: "Hello World: 14"
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