There is no way to "convert" logic bricks. They are native code and have much more connections to the BGE core code thatthan Python has.
Mimic an action actuator
You might mimic the action actuator with playAction().
Dynamically configure action actuators
Your question sounds like you want to either dynamically change the configuration while the game is running e.g. setup a different action, or you do not want to use the GUI to setup a lot of actions to play.
In both situations you can still use one or more pre-set action actuators. The BGE API of the BL_ActionActuator allows you to change the configuration of each of them on the fly. Do not forget you need to activate them after configuration change.
I hope it helps