reccomending, according to the selected listbox value

[Yoriz]

Inside the function def getRecommendations(prefs, person, similarity = sim_pearson):
its expecting the passed in prefs to be an object that can be iterated

for other in prefs:

you are calling this method with b=getRecommendations(STproject.dictionary,STproject.selected,similarity=sim_distance)
it looks like you want to be calling the instance instead of the class
b=getRecommendations(self.dictionary,self.selected,similarity=sim_distance)
The method dictionary does not return a iterable of prefs and the method selected does not return a person.