How to return a boolean value regarding success and still include the http status code in python?

Question

I want to be able to return success when a method call succeeds but still be able to return the http error code when it fails.

Obviously the only numeric value that evaluates as False is 0, so returning http codes as numerics will evaluate all of them as true.

I have the impression that the solution is to return an object that evaluates as true only for 200-2xx values and that also converts to number so people can compare it.

Are you aware about anyone that had a similar approach? -- I don't like the idea of raising exceptions in this case.

Answer 1

Just return two results, the success flag and the http response:

def some_function():
    return success, http_response

and use tuple assignment:

success, response = some_function()
if success:

The approach that the requests module takes is to return a response object always, then give you the choice of raising an exception based on the response code:

response = requests.get(url)
response.raise_for_status()

where the Response.raise_for_status() method gives users of your API the option to raise an exception. The other option is to test for the status code:

if not 200 <= response.status_code <= 299:
    # problem status response

Both of these approaches have the advantage that they are explicit. Don't try to overload a return value with multiple meanings. If a HTTP response outside the 2xx range is an exception, treat it as such by raising an exception.

Answer 2

I'm not sure what you mean, but I assume you just want to catch Http errors. In that case, is this what you mean? (I usually use the build in module "urllib2" to do http requests/ open urls)

 import urllib2
 try:
    urllib2.urlopen(url) #open a url
 except urllib2.HTTPError, err:
    if err.code == 404:
            print "Page not found!"
    elif err.code == 403:
        print "Access denied!"
    else:
        print "Something happened! Error code", err.code
 except urllib2.URLError, err:
    validationerror = err
    print(" ")
    print("Connection error")
    print(err)
    print "Can not connect to annotation review server"
    print(" ")
 except:
    validationerror = (sys.exc_info()[0])
    print(validationerror)

Answer 3

It's not Pythonic to rely on return values to indicate success/failure, especially in a function that's supposed to return something in the first place.

Just return the HTTP code. If the function fails, raise an exception (create a custom exception -- TimeoutError, UnknownHostError... and make the HTTP code one of its attributes).

In addition, take a look at what the Requests library (http://requests.readthedocs.org) does. Response objects have a raise_for_status method, which will raise an exception if their HTTP code isn't in the 2xx range.