Get ROS2 message fields from Python messages?

edit

Looking at the latest ROS2 master code, it looks like you can currently get the names of the message fields from __slots__, but not the types:

>>> import std_msgs.msg
>>> x = std_msgs.msg.Header()
>>> dir(x)
['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__slots__', '__str__', '__subclasshook__', '_frame_id', '_stamp', 'frame_id', 'stamp']
>>> print(x.__slots__)
['_stamp', '_frame_id']
>>>

ROS 2 Crystal does have that information: MessageClass.get_fields_and_field_types() (see https://github.com/ros2/rosidl_python... )

Note that the API and returned information for this kind of introspection is likely going to change in the next ROS 2 release (Dashing) so check the migration in the future to check for information.