There are few things in python you do not learn till it punches you in the face. Mutable data types. I started using python 6 months back and "assumed" arguments are passed by value. One example where this mutable argument can behave in a way that you do not expect it to be is if you have lets say "[]" as a default argument of function. Example:
def myfunc( input=[] ) blah blah

This does something bad and Quantified Code detects this. They point out that this is not what you expect. They suggest better ways to achieve the same. This is good stuff.

One piece of advise is to not to try fix everything that QC suggests. Fix the dangerous ones. Do not become a victim if instantaneous gratification QC provides.