I have a BaseHandler class that subclasses the Tipfy RequestHandler in my AppEngine site. In it, I have setup a "poor man's" browser sniffer for mobile devices with a class attribute (a tuple) containing device names.
In a subsequent method, I loop through the device names in the tuple and check them against the user agent string from the Request object. If I get a match, I set an instance attribute called "is_mobile" to True.
In that method, however, Python is giving me a "TypeError: argument of type 'UserAgent' is not iterable" error, and I can't understand why, since the line it is complaining about is not (as far as I understand) a loop.
Here is the code:
class BaseHandler(RequestHandler, AppEngineAuthMixin, AllSessionMixins):
mobile_devices = ('Android', 'iPhone', 'iPod', 'Blackberry')
....
def detect_mobile_devices(self):
found_device = False
for device in self.__class__.mobile_devices:
if device in self.request.user_agent:
found_device = True
break
self.is_mobile = found_device
Here is the line Python does not like:
File "/path/to/project/app/apps/remember_things/handlers.py", line 56, in detect_mobile_devices
if device in self.request.user_agent:
The expression
device in self.request.user_agent
will first try to call
self.request.user_agent.__contains__(device)
If this method does not exist, Python tries to iterate over self.request.user_agent and compares each item it encounters to device. Obviously, the type of self.request.user_agent neither allows .__contains__() nor iteration, hence the error message.