List of tuples as argument in ROS2 launch

Question

I'd like to define an argument in ROS2 launch file which is a list of tuples. How should the list in default_value be formatted?

def generate_launch_description():
   argument = LaunchConfiguration('argument', default_value=[(1, 0, 0), (0, 1, 0), (0, 0, 1)])
   node = Node(package='...', executable='...', parameters=[{'argument': argument}])
   return node, argument

Currently, I'm getting the following errors based on different formatting:

argument.default_value = [(1, 0, 0), (0, 1, 0), (0, 0, 1)]
>>> Failed to normalize given item of type '<class 'tuple'>', when only 'str' or 'launch.Substitution' were expected.

argument.default_value = ['(1, 0, 0)', '(0, 1, 0)', '(0, 0, 1)']
>>> In the node argument.value[0] is '(' whereas it should be (1, 0, 0). 

Answer 1

I found a solution which works yet is not perfect. When the argument value in the launch file is formatted as:

argument.default_value = "['(1, 0, 0)', '(0, 1, 0)', '(0, 0, 1)']"

the argument is passed to the node as:

argument.value[0]
>>> '(1, 0, 0)'

eval(argument.value[0])
>>> (1, 0, 0)

If anyone knows a way to skip eval(..) by passing Tuple directly, that'd be better.