I'd like to raise a Python-standard exception when an HTTP response code from querying an API is not 200, but what specific exception should I use? For now I raise an OSError:
if response.status_code != 200:
raise OSError("Response " + str(response.status_code)
+ ": " + response.content)
I'm aware of the documentation for built-in exceptions.
You can simply call Response.raise_for_status() on your response:
>>> import requests
>>> url = 'http://stackoverflow.com/doesnt-exist'
>>> r = requests.get(url)
>>>
>>> print r.status_code
404
>>> r.raise_for_status()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "requests/models.py", line 831, in raise_for_status
raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 404 Client Error: Not Found
This will raise a requests.HTTPError for any 4xx or 5xx response.
See the docs on Response Status Code for a more complete example.
Note that this does not exactly do what you asked (status != 200): It will not raise an exception for 201 Created or 204 No Content, or any of the 3xx redirects - but this is most likely the behavior you want: requests will just follow the redirects, and the other 2xx are usually just fine if you're dealing with an API.
The built-in Python exceptions are probably not a good fit for what you are doing. You will want to subclass the base class Exception, and throw your own custom exceptions based on each scenario you want to communicate.
A good example is how the Python Requests HTTP library defines its own exceptions:
In the event of a network problem (e.g. DNS failure, refused connection, etc), Requests will raise a
ConnectionErrorexception.In the rare event of an invalid HTTP response, Requests will raise an
HTTPErrorexception.If a request times out, a
Timeoutexception is raised.If a request exceeds the configured number of maximum redirections, a
TooManyRedirectsexception is raised.All exceptions that Requests explicitly raises inherit from
requests.exceptions.RequestException.
ValueErrorwould be appropriate. I can't think off the top of another built-in exception that would apply (aside form Exception :p) so you'd probably want to craft your own exceptions in that case as the accepted answer suggests.