requests is very useful, but it always gets mentioned as a good python codebase and I'm not sure I agree. One example:

The first thing many users will do is

requests.get?

Which tells them that it takes some kwargs, but doesn't tell them what those kwargs are. It's easy, especially for a newcomer, to read "optional arguments that `request` takes" and fail to understand that they should look up the docs on (not-really-encouraged-as-part-of-public-API) function `request`. That's pretty bad; those kwargs are important! (The reason is because requests.get is implemented as a call to request(method, ..., kwargs) but the user doesn't care what the implementation-level reason is.)

Beyond that I did look into the codebase once to investigate a possible bug and there were a few python style things I wanted to fix, but I don't remember them so this comment probably sounds kind of annoying (it would annoy me if I were reading it not writing it...). It didn't strike me a really clean codebase. But yes the library is very useful and I'm sure it's a pretty decent python codebase.

>>> requests.get?
Signature: requests.get(url, params=None, **kwargs)
Docstring:
Sends a GET request.

:param url: URL for the new :class:`Request` object.
:param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`.
:param \*\*kwargs: Optional arguments that ``request`` takes.

Here are all the kwargs the user probably wanted to know but failed to find out and was forced to either browse online docs or the source code:

def request(method, url, **kwargs):
"""Constructs and sends a :class:`Request <Request>`.
:param method: method for the new :class:`Request` object.
:param url: URL for the new :class:`Request` object.
:param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`.
:param data: (optional) Dictionary, bytes, or file-like object to send in the body of the :class:`Request`.
:param json: (optional) json data to send in the body of the :class:`Request`.
:param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`.
:param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`.
:param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': ('filename', fileobj)}``) for multipart encoding upload.
:param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth.
:param timeout: (optional) How long to wait for the server to send data
before giving up, as a float, or a (`connect timeout, read timeout
<user/advanced.html#timeouts>`_) tuple.
:type timeout: float or tuple
:param allow_redirects: (optional) Boolean. Set to True if POST/PUT/DELETE redirect following is allowed.
:type allow_redirects: bool
:param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
:param verify: (optional) if ``True``, the SSL cert will be verified. A CA_BUNDLE path can also be provided.
:param stream: (optional) if ``False``, the response content will be immediately downloaded.
:param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
:return: :class:`Response <Response>` object
:rtype: requests.Response