In this article we’ll look at a how to make a minimal device-aware web
application. The point of this article is not to demonstrate a useful
application but rather to show just how little code is required to make an app
that is fully device aware, and that can change its presentation entirely
depending on the nature of the device accessing it.
To keep things simple and lightweight we’ll use Python in conjunction with
web.py and DeviceAtlas
Personal (the cloud-based version of DeviceAtlas).
Web.py is a minimalist
Python web framework that suits this example because it is simple and
lightweight but the techniques demonstrated here will work equally well in any
other web framework. You will need to install web.py if you want to run this example.
easy_install web.py
DeviceAtlas Personal is a device detection web service
that requires no installation, configuration or maintenance – it just
works. To make this easier to incorporate into a Python project I’ve attached a
Python module to this article that wraps the web service into a convenience
function that does everything you need.
Without further ado, here is the code:
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import web from DeviceAtlas import DaPersonal urls = ( '/', 'index',) app = web.application(urls, globals()) pageTemplate = '<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd"><html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>test page</title></head><body><p>Hello, %s user</p><p>%s</p></body></html>' class index: def GET(self): props = DaPersonal.get_device_properties(web.ctx.env['HTTP_USER_AGENT']) if props.has_key('mobileDevice') and props['mobileDevice']: return pageTemplate % ('mobile', props) else: return pageTemplate % ('sedentary', '') if __name__ == "__main__": app.run() |
Run the server as follows:
python test_app.py
Now, accessing the URL http://localhost:8080/ will result in two different
outputs:
Desktop browser
Hello, sedentary user
Mobile browser
Hello, mobile user
{u’mobileDevice’: True, u’isBrowser’: False, u’displayWidth’: 320,
u’displayHeight’: 480, ‘_source’: ‘cache’}
Notes
-
Caching – DeviceAtlas Personal is best used in conjunction with local caching to avoid
the delay incurred by the round-trip to our servers. For new devices that have
not been seen before and hence are not in the cache, the detection time is
typically in the order of 500ms; for previously-seen (cached) devices it is
unmeasurably small (less than 1ms). Caching is enabled by default in the module
but you will need to create the appropriate directory for it (typically
/tmp/DeviceAtlasCache). - DeviceAtlas Personal – this is a preview version of the service, and right now we make no guarantees about stability, performance, or uptime.
- Deployment &ndash this application can be run as a standalone application that implements its own HTTP stack, or run as a CGI, or WSGI, or mod_python application with Apache / Lighttpd / nginx
Closing Comments
This is an extremely simple application, clearly, but it nonetheless demonstrates a couple of key points:
- Device adaptation need not be complex. In this application cloud-based detection has completely removed this burden, and yet is accurate and very fast
- Adapting websites do not necessarily require complex frameworks and lots of code
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