How to scan as fast as ping-viewer in python

From my experiment, in Ping-viewer, Ping360 can scan 20 beams for one second. While when I keep all the parameters the same, and use transmitAngle(self, angle) in python, I can only scan 11 beams for one second.
I guess the reason is "in ping-viewer" we only have one command to scan a certain area. While in transmitAngle, we have arbitrary scan direction which have one command for each direction. Thus an arbitrary scan will have more delay.
So I wonder whether my guess is correct and how I can scan as fast as in ping-viewer (only scan certain area in the front of sonar)?
I appreciate your kindly help.
Thanks.