If you have two motors on one motor bridge, here is sample code for how you can move forward. There are many ways to feed the robot commands like making a list of them or communicating directly with the robot with UDP or TCP/IP. I used an indirect method with AJAX and storing the next command on a web server. Here is a video of my robot moving.
The lag in response is because I'm slowly punching in the commands on my webserver (located in Canada) while the robot fetches them (from Japan). The waddle as it moves forward is hardly detectable. It is running without the 5 ohm resistor, and the right and left turns are also operated in pulses so that they aren't too much more powerful than the forward drive. You'll notice the wheels are different in the video because the treads (seen in the other photos) were too weak to support the weight of a laptop reliably. More about the project can be found here.
###initialize the serial connection
#for windows (change COM6 to match the USB device)
#ser = serial.Serial("COM6", 2400)
#for linux (change /dev/ttyUSB0 to match the USB device)
ser = serial.Serial("/dev/ttyUSB0", 2400)
ser.open() #open the connection
#Make sure RTS and DTR are off
### function to waddle forward (for one motor bridge with two motors)
while times > 0:
times -= 1
c = 1