How do I go about printin a NoneType object in Python?

# score can be a NonType object
logging.info("NEW_SCORE : "+score)

Also why is that sometime I see a comma instead of the + above?

The best approach is:

logging.info("NEW_SCORE: %s", score)

In most contexts, you'd have to use a % operator between the format string on the left and the value(s) on the right (in a tuple, if more than one). But the logging functions are special: you pass the format string as the first argument, then, one after the other, just as many arguments as needed to match the number of %s &c formatting markers in the format, and the logging functions will use the formatting operator %s as appropriate if and only if necessary -- so you don't incur any runtime overhead if your current logging level is such that, e.g., logging.info is not actually going to be shown.

Forget str calls and +-based string concatenation anyway -- even without logging's specials, %-formatting is really the way to go (in Python 2.6 or earlier; in 2.6 or later, you should also consider strings' format method, allowing clearer and more readable expression of what amounts to the same functionality).