Pywunder is a very simple wrapper around the wunderground weather API, at this stage it is mostly incomplete, providing only very simple access to the forecasts api.
To use it do the following:
>>> import pywunder
>>> client = pywunder.Client("your api key")
>>> forecasts = client.forecast("UK/London") #Gives you a four day forecast
>>> forecasts[0].description
u'Clear in the morning, then partly cloudy. High of 16C. Breezy. Winds from the SW at 15 to 20 km/h.'