create_instructor_answer errors on string cid input

[kwshi]

per create_instructor_answer's current documentation the post parameter can be either a string (the post's cid) or dictionary (post object with id key).

piazza-api/piazza_api/network.py

Lines 192 to 211 in acb5de9

	def create_instructor_answer(self, post, content, revision, anonymous=False):
	"""Create an instructor's answer to a post `post`.
	It seems like if the post has `<p>` tags, then it's treated as HTML,
	but is treated as text otherwise. You'll want to provide `content`
	accordingly.
	:type post: dict|str|int
	:param post: Either the post dict returned by another API method, or
	the `cid` field of that post.
	:type content: str
	:param content: The content of the answer.
	:type revision: int
	:param revision: The number of revisions the answer has gone through.
	The first responder should out 0, the first editor 1, etc.
	:type anonymous: bool
	:param anonymous: Whether or not to post anonymously.
	:rtype: dict
	:returns: Dictionary with information about the created answer.
	"""

however passing in a string post actually causes an error/crash: that's because

piazza-api/piazza_api/network.py

Lines 212 to 215 in acb5de9

	try:
	cid = post["id"]
	except KeyError:
	cid = post

doesn't handle the type cases correctly. trying to index ["id"] in a string raises a TypeError not a KeyError so it doesn't get caught, and the fallback doesn't work. one possible fix is to catch the TypeError, as is done in some other functions, e.g. update_post:

piazza-api/piazza_api/network.py

Lines 259 to 275 in acb5de9

	def update_post(self, post, content):
	"""Update post content by cid
	:type post: dict|str|int
	:param post: Either the post dict returned by another API method, or
	the `cid` field of that post.
	:type subject: str
	:param content: The content of the followup.
	:rtype: dict
	:returns: Dictionary with information about the updated post.
	"""
	try:
	cid = post["id"]
	except KeyError:
	cid = post
	except TypeError:
	cid = post

another fix is to just simplify the API and only take in string post ID instead of str|dict|int; after all that is the only part of the post object needed, so it doesn't logically make sense to require the whole object. for most people typing out an additional ["id"] is not all that much added work, and the benefit is that the API is a lot more consistent and well-typed this way.