Inconsistent Serial Fails

I am trying to develop a python tkinter based app that would read the data from my arduino sensor platform. I am getting inconsistent errors that i can't understand why this happen

Solution 1:

I would ask myself about your setup (which I don't know what the circuit is):

1. have you tested your code with test data that works independently of a link to your Arduino.
2. have you checked the validity of the data coming from the Arduino.
3. what measures are you taking to avoid noise being introduce with your data input.