First part, should be pretty straightforward.
Code:
wire = wpilib.I2C(wpilib.I2C.Port.kOnBoard, 4)
Second part -- I admit the docs aren't super clear here, but it wants you to pass it a list of things that can be converted to bytes... so either integers or a bytestring.
Code:
wire.transaction(b'go', 0)
I'm pretty sure that'll work.
It's weird that the java code isn't trying to receive any data (maybe writeBulk is more appropriate?).