add_header expecting 3 arguments instead of just key/value

Question

I'm encountering this error message:

TypeError: add_header() takes exactly 3 arguments (2 given)

when using these parameters:

testService("SomeServiceName", "POST", "[redacted valid url]", ('Content-type','application/json'), [redacted valid json])

Normally this error means I'm not passing "self" as a parameter, but seeing as this method is not being called in a class, I'm not sure what to do. I've tried passing self in as a parameter in both the parameters and inside the method. And I've tried wrapping the header in brackets and parentheses. When I pass "self" I get the error message that self is undefined, and when I use the brackets instead of parentheses, I get the same error as above.

Anyone with magical Python debugging skills out there? Thanks so much for taking the time to check this out!

def testService(name, verb, url, header="", requestBody=""):

#Log out the name of the request we're testing
if (name is not None) or (name.strip() is not ""):
    print "Checking  " + name + "\n\n"

    # Make URL with StoreNumber
    if (url is not None) or (url is not ""):
        testUrl = url

        # If specified verb is GET
        if verb.strip().upper() == "GET":

            # Create request
            req = urllib2.Request(testUrl)
            print "Making request with URL: " + testUrl + "\n\n"

            # Send request
            try:
                response = urllib2.urlopen(req)

                # If service returns 200 Okay
                print "Connection to " + name + " Service successful. Returned with code " + str(response.code) + "\n\n"

                # Log response
                print "Response: " + response.read() + "\n\n"


                # Handle exceptions
                # If HTTP Error
            except HTTPError as e:
                if hasattr(e, 'reason'):
                    print name + ' failed to reach a server.'
                    print 'Reason: ', e.reason

                elif hasattr(e, 'code'):
                    print e.code

                elif hasattr(e, 'message'):
                    print e.message
                pass 

            # If URL was the problem
            except URLError as e:
                if hasattr(e, 'reason'):
                    print name + ' failed to reach a server.'

                    if str(e.reason) == "[Errno 11004] getaddrinfo failed":
                        print "[Errno 11004] getaddrinfo failed with bad url: " + testUrl + "\n\n"

                    else:
                        print 'Reason: ', e.reason

                elif hasattr(e, 'code'):
                    print 'Error code: ', e.code

                elif hasattr(e, 'message'):
                    print e.message
                pass 


        # If specified verb was POST
        elif verb.strip().upper() == "POST":

            # Check for None requestBody
            if (requestBody is not None) or (requestBody.strip() is not ""):
                data = urllib.urlencode(requestBody)

                # Create request
                req = urllib2.Request(testUrl, data)

                # Check for header
                if (header is not None) or (header.strip() is not ""):
                    req.add_header(header)

                    # YO YO THE BELOW CODE IS INCOMPLETE PLEASE FINISH
                    # Log request with URL and Data
                    print "Making request with URL: " + testUrl + " and data: THIS PART IS UNFINISHED PLEASE FINISH ME \n\n" 

                    try: 
                        response = urllib2.urlopen(req)

                        # If service returns 200 Okay
                        print "Connection to " + name + " Service successful. Returned with code " + str(response.code) + "\n\n"

                        # Log response
                        print "Response: " + response.read() + "\n\n"


                    # Handle exceptions
                    # If HTTP Error
                    except HTTPError as e:
                        if hasattr(e, 'code'):
                            print e.code
                        elif hasattr(e, 'message'):
                            print e.message
                        elif hasattr(e, 'reason'):
                            print name + ' failed to reach a server.'
                            print 'Reason: ', e.reason
                        pass 

                    except URLError as e:
                        if hasattr(e, 'reason'):
                            print name + ' failed to reach a server.'

                            if str(e.reason) == "[Errno 11004] getaddrinfo failed":
                                print "[Errno 11004] getaddrinfo failed with bad url: " + url + "\n\n"
                            else:
                                print 'Reason: ', e.reason                
                        elif hasattr(e, 'code'):
                            print 'Error code: ', e.code

                        elif hasattr(e, 'message'):
                            print e.message
                        pass 

                # Header non-existent in testService call
                else: 
                    print "Service header not provided. Exiting program"
                    sys.exit() 

            # Requesty Body not present in testService call
            else:
                print "Service request body not provided in code. Exiting program"
                sys.exit()

        # If specified verb is not supported (Currently only GET and POST are supported)    
        else:
            print name + " Service written with HTTP verb other than GET or POST. Exiting program"
            sys.exit()

    else:
        print "Service url not provided in code. Exiting program"
        sys.exit() 


else: 
    print "Service name not provided in code. Exiting program"
    sys.exit()

Answer 1

From the documentation, add_header takes two arguments. You are calling it with one argument, a tuple with two values.

What you should do:

req.add_header(key, value)

What you are currently doing because you are getting the header as a tuple:

req.add_header((key, value,))    # aka passing a tuple with both arguments to the key parameter

You need to unpack the tuple:

req.add_header(header[0], header[1])

Or even better, using the splat operator (*):

req.add_header(*header)      # Does the same thing as above

Also, you are using an empty string as the default argument for header, when when it is supplied it is a tuple. You should probably change the default value to a tuple or None.

Answer 2

Your header is a 2-tuple:

('Content-Type', 'application/json')

You're trying to do this:

req.add_header('Content-Type', 'application/json')

But in reality you're doing this:

req.add_header(('Content-Type', 'application/json'))

Notice that you're only passing one argument - a tuple - instead of two, a key and a value.

To fix, unpack your header when you pass it with the * (informally, 'splat') operator:

req.add_header(*header)