WURFL and Python

Check the documentation for more information.

Serialization

It's also possible to serialize changes that you make to a WURFL compatible xml file.

from wurfl import devices
from pywurfl.serialize import Serialize

# Remove some groups and their capabilities from the WURFL hierarchy
devices.remove_group('j2me')
devices.remove_group('mms')

Serialize(devices).to_xml("no_j2me_or_mms.xml")

Search Algorithm Classes

The algorithms module contains three algorithm classes (Tokenizer, JaroWinkler and LevenshteinDistance). When instantiating any of these classes, a callable object will be returned that can be used to search a 'devices' object with the provided user agent.

Tokenizer([devwindow])

The devwindow argument determines the upper limit of device matches before the algorithm would return the generic device.

JaroWinkler([accuracy=1.0], [weight=0.05])

The accuracy argument determines the lower limit at which pywurfl will determine if a user agent matches another. If no device can be found that scores equal to or greater than accuracy, a generic device is returned. Valid values are between 0.0 and 1.0

LevenshteinDistance()

from wurfl import devices
from pywurfl.algorithms import JaroWinkler, Tokenizer, LevenshteinDistance

tokenizer = Tokenizer()
jarow = JaroWinkler()
levdis = LevenshteinDistance()

user_agent = "Nokia3350/1.0 (05.15)"
device1 = jarow(user_agent, devices)
device2 = tokenizer(user_agent, devices)
device3 = levdis(user_agent, devices)

device4 = devices.select_ua(user_agent, search=jarow)
device5 = devices.select_ua(user_agent, search=tokenizer)
device6 = devices.select_ua(user_agent, search=levdis)

It's also very easy to define your own algorithm for use in pywurfl in case the algorithms provided don't serve your needs. Just subclass the pywurfl.algorithms.Algorithm class and follow the protocol.

Device Objects

The object returned by either select_id or select_ua is usually a Device instance.

device = devices.select_id(string)

A device object has many attributes. The device id, user agent, fall_back and actual_device_root attributes are exposed with the following attributes of the device object:

device.devid
device.devua
device.fall_back # All devices have a fall_back attribute
device.actual_device_root

Any capability that is defined in the WURFL becomes an attribute of the device object. For example:

device.brand_name
device.model_name
device.ringtone

All attributes are converted into their respective Python types. For example:

device.ringtone  # Attribute is boolean
device.preferred_markup  # Attribute is a string
device.rows  # Attribute is an integer

You can iterate over a device object to select each capability and its corresponding value. For example, to print out all capabilities of a device object you can use the code below:

for capability, value in device:
    print capability, value

Every device has a shared groups attribute which is a Python dictionary where the keys are the capability group names as defined in the WURFL and the values are lists of the capability names for that specific group.

for group in sorted(device.groups):
    print group

Classes vs. Instances

The API methods can also return a class object instead of an instance. What wurfl2python does is produce a module that creates a single inheritance class hierarchy of all WURFL devices. You can use this to your advantage if you want to change the attributes of a device at run-time and have all of its descendants represent that change.

# get an arbitrary device instance
device = devices.select_id('blackberry_generic_ver3_sub2')

# get the generic device *class*
gen = devices.select_id('generic', instance=False)

# modify the generic class
gen.teleportation_device = False

# since all devices inherit from the generic device, this will not raise an attribute error now
device.teleportation_device # == False

If you want to maintain the integrity of the class hiearchy, you should use the add/remove/insert API methods on the 'devices' object mentioned above.

Query Language

The pywurfl package includes a query language that makes it easier to retrieve a list of devices, WURFL IDs or user agents based on the capabilities of a device. The best way to see what the query language looks like and what it can do is with an example.

from wurfl import devices
from pywurfl.ql import QL  # Import the query function generator

# Retrieve a function that will query the devices object
query = QL(devices)

# QL also adds a query method to devices (devices.query)

q1 = """select id where ringtone=true and rows < 5 and
        columns > 5 and preferred_markup = 'wml_1_1'"""

for wurfl_id in query(q1):
    print wurfl_id


# Let's look for some nice phones
q2 = """select device where all(ringtone_mp3, ringtone_aac, wallpaper_png,
        streaming_mp4) = true"""

# Notice that we can also retrieve device classes
for device in devices.query(q2, instance=False):
    print device.brand_name, device.model_name

A full description of the query language is included in the documentation.

The WURFL Processor

The WURFL processor is a general class that walks a WURFL xml file and executes hooks as specific events occur in a fashion similiar to SAX. The best way to understand the WURFL processor is to look at its documentation. For an example of how to use use it, look at the source for wurfl2python.py.

Contributors

Thanks to Pau Aliagas (pau at newtral dot org) for the many patches, bug reports and improvements.