Unable to publish float fields with ros2 topic pub

edit

Here's the command line and the result:

pierce@ros2-terminal:~/ssp_ws$ ros2 topic pub /att ssp_interfaces/msg/Attitude "{yaw:1.0}"
Failed to populate field: 'Attitude' object has no attribute 'yaw:1.0'

Tbh your response to Mike trying to help made me almost skip your question, but you're missing a space:

{yaw:1.0}

isn't valid yaml:

ERROR:

while scanning a plain scalar
  in "<unicode string>", line 1, column 2:
    {yaw:1.0}
     ^
found unexpected ':'
  in "<unicode string>", line 1, column 5:
    {yaw:1.0}
        ^
Please check https://pyyaml.org/wiki/YAMLColonInFlowContext for details

if you change it to {yaw: 1.0} it should work.

According to http://design.ros2.org/articles/idl_i..., there is no native type named float32.