The first thing you need to get is a list of the Dedicated Hosts on your account. To list the Dedicated Hosts on your account you can use the following code:
import SoftLayer
from pprint import pprint as pp
client = SoftLayer.Client()
dedicatedHosts = client['SoftLayer_Account'].getDedicatedHosts()
pp(dedicatedHosts)
Once you have the Dedicated Host ID you want to migrate the Virtual Guest to you can use this script to kick of an immediate migration of the Virtual Guest.
"""
@author Ryan TIffany
"""
import SoftLayer
from pprint import pprint as pp
destinationHostId = 987654
vsiId = 1234567
client = SoftLayer.Client()
migrateGuest = client['SoftLayer_Virtual_Guest'].migrateDedicatedHost(destinationHostId, id=vsiId)