What does the data you're getting out look like?
Is it printing byte values rather than the string representations of them? That's what was being talked about above to make it faster, I think.
But I'm not sure whether your python script is aware of that, or thinks it's getting numbers as strings.
Before involving a second point of failure (your python script) you should know what is being send down the wire.
Connect to it using a nice serial terminal program (I like hterm) that lets you show the data as ASCII or hex/binary/decimal, so you can see for sure what it's sending out/.