Why is collections.Counter uppercase and collections.defaultdict is not?

Question

Some of the elements in the collections module seem to be uppercase, some other not. Is there a specific rationale behind it?

Answer 1

According to this reddit comment

All classes written in python are upper camel case.

All types based on C code are lower. [like the primitives]

namedtuple is a function, thus follows the naming convention of functions. deque and defaultdict are types, (C); Counter and OrderedDict are classes, (Python).