Updating multiple custom properties from a list

I am using NPM 11.5.3 and trying to update multiple custom properties on a node through the use of SWIS Update and Python 2.7

custompropertylist = ['prop1', 'prop2', 'prop3']

for property in custompropertylist:

     value = raw_input("%s:" % prop)

     swis.update(uri + '/CustomProperties', property=value)

I have this successfully working if I don't use a list and manually define each property and execute, but I am trying to make my code more modular. I have tried tinkering with this for a bit without success and the only return value of SWIS Update I get is 'None'