Naming convention in Collections: why are some lowercase and others CapWords?

Question

Why the mixture of lowercase and UpperCamelCase?

namedtuple
deque   
Counter 
OrderedDict
defaultdict

Why collections instead

Answer 1

The collections module follows the PEP 8 Style Guide:

Modules should have short, all-lowercase names.

This is why it's collections

---

Almost without exception, class names use the CapWords convention.

This is why it's Counter and OrderedDict, because they are both classes:

>>> collections.Counter

>>> collections.OrderedDict

---

namedtuple is a function, so it does not follow the style guide mentioned above. deque and defaultdicts are types, so they also do not:

>>> collections.deque

>>> collections.namedtuple

>>> collections.defaultdict

---

Note: With Python 3.5, defaultdict and deque are now classes too:

>>> import collections
>>> collections.Counter

>>> collections.OrderedDict

>>> collections.defaultdict

>>> collections.deque

I assume they kept defaultdict and deque lowercase for backwards compatibility. I would not imagine they'd make such a drastic name change for the sake of a style guide.