I have a number of classes and corresponding feature vectors, and when I run predict_proba() I will get this:
classes = [\'one\',\'two\',\'three\',\'one\',\'
As a rule, any attribute in a learner that ends with _ is a learned one. In your case you're looking for clf.classes_.
clf.classes_
Generally in Python, you can use the dir function to find out which attributes an object has.
dir