params.yaml

talker:
  ros__parameters:
    some_int: 42
    a_string: "Hello world"
    a_bool: true
    some_lists:
      some_integers: [1, 2, 3, 4]
      some_doubles : [3.14, 2.718]
      some_more_lists:
        verse1: ["a", "b", "c"]
        verse2: [1, 2, 3]
        verse3:  ["you", "and", "me"]
    more_int: 42
    more_string: "Hello world"
    bool_list: [true, true, false]
    #invalid_params: [1, 'a', 2]

paramsnode.py

import sys

import rclpy
from rclpy.node import Node
from rclpy.parameter import Parameter


class ParamsNode(Node):

    def __init__(self):
        super().__init__('paramsnode')
        self.set_parameters([
            Parameter('some_int', Parameter.Type.INTEGER, 42),
            Parameter('a_string', Parameter.Type.STRING, 'hello'),
            Parameter('a_bool', Parameter.Type.BOOL, True),
            Parameter('some_lists.some_integers', Parameter.Type.INTEGER_ARRAY, [1,2,3]),
            Parameter('some_lists.some_doubles', Parameter.Type.DOUBLE_ARRAY, [1.0,2.0,3.0]),
            Parameter('some_lists.some_more_lists.verse1', Parameter.Type.STRING_ARRAY, ['a', 'b', 'c']),
            Parameter('some_lists.some_more_lists.verse2', Parameter.Type.INTEGER_ARRAY, [1, 2, 3]),
            Parameter('some_lists.some_more_lists.verse3', Parameter.Type.STRING_ARRAY, ['you', 'and', 'me']),
            Parameter('more_int', Parameter.Type.INTEGER, 13),
            Parameter('more_string', Parameter.Type.STRING, 'xaphod'),
            Parameter('bool_list', Parameter.Type.BOOL_ARRAY, [True, True, False]),
            #Parameter('invalid_params', Parameter.Type.INTEGER_ARRAY, [1, 'a', 2]),
        ])

def main(args=None):
    if args is None:
        args = sys.argv

    rclpy.init(args=args)

    node = ParamsNode()

    rclpy.spin(node)

    node.destroy_node()
    rclpy.shutdown()


if __name__ == '__main__':
    main()