capitalization of library class names

Question

Why do collection.defaultdict and collection.OrderedDict have different capitalizations?

Is there some subtle difference that I should be a

Answer 1

Usually, that is in accordance with good style, classes are capitalised.

def MyClass (object):
    pass

my_instance = MyClass()

like this.

You should read this document about it: http://www.python.org/dev/peps/pep-0008/