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Python migration guide from ROS 1

Node Initialization

# rospy.init_node('asdf')
rclpy.init(args=sys.argv)
node = rclpy.create_node('asdf')
# rospy.loginfo('Created node')
node.get_logger().info('Created node')

ROS Parameters

# port = rospy.get_param('port', '/dev/ttyUSB0')
# assert isinstance(port, str), 'port parameter must be a str'
port = node.declare_parameter('port', '/dev/ttyUSB0').value
assert isinstance(port, str), 'port parameter must be a str'
# buadrate = rospy.get_param('baudrate', 115200)
# assert isinstance(port, int), 'port parameter must be an integer'
baudrate = node.declare_parameter('baudrate', 115200).value
assert isinstance(port, int), 'port parameter must be an integer'
# rospy.logwarn('port: ' + port)
node.get_logger().warn('port: ' + port)

Creating a Publisher

# pub = rospy.Publisher('chatter', String)
pub = node.create_publisher(String, 'chatter')

Creating a Subscriber

# sub = rospy.Subscriber('chatter', String, callback)
sub = node.create_subscription(String, 'chatter', callback)

Creating a Service

# srv = rospy.Service('add_two_ints', AddTwoInts, add_two_ints_callback)
srv = node.create_service(AddTwoInts, 'add_two_ints', add_two_ints_callback)

Creating a Service Client

# rospy.wait_for_service('add_two_ints')
# add_two_ints = rospy.ServiceProxy('add_two_ints', AddTwoInts)
# resp = add_two_ints(req)
add_two_ints = node.create_client(AddTwoInts, 'add_two_ints')
while not add_two_ints.wait_for_service(timeout_sec=1.0):
    node.get_logger().info('service not available, waiting again...')
resp = add_two_ints.call_async(req)
rclpy.spin_until_future_complete(node, resp)