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

defaultdict is written in C and pep8 don't apply , in the other hand OrderDict is written in python,

you can read C code norm for the C implementation of Python here : PEP 7

reference : source code python2.7

defaultdict  : Modules/_collectionsmodule.c
OrderDict : Lib/collections.py

Answer 2

The capitalization of the class names is irrelevant, it doesn't signify anything. Except that Python has sometimes grown organically and the standard library doesn't have the same homogenous feel as other large libraries such as the Win32 API or the Java standard library.

Answer 3

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/