Collective Intelligence with Python 1

We have a base of data first

recommendations.py

critics={'Lisa Rose': {'Lady in the Water': 2.5, 'Snakes on a Plane': 3.5, 'Just My Luck': 3.0, 'Superman Returns': 3.5, 'You, Me and Dupree': 2.5, 'The Night Listener': 3.0},'Gene Seymour': {'Lady in the Water': 3.0, 'Snakes on a Plane': 3.5, 'Just My Luck': 1.5, 'Superman Returns': 5.0, 'The Night Listener': 3.0, 'You, Me and Dupree': 3.5},'Michael Phillips': {'Lady in the Water': 2.5, 'Snakes on a Plane': 3.0, 'Superman Returns': 3.5, 'The Night Listener': 4.0},'Claudia Puig': {'Snakes on a Plane': 3.5, 'Just My Luck': 3.0, 'The Night Listener': 4.5, 'Superman Returns': 4.0, 'You, Me and Dupree': 2.5},'Mick LaSalle': {'Lady in the Water': 3.0, 'Snakes on a Plane': 4.0, 'Just My Luck': 2.0, 'Superman Returns': 3.0, 'The Night Listener': 3.0, 'You, Me and Dupree': 2.0},'Jack Matthews': {'Lady in the Water': 3.0, 'Snakes on a Plane': 4.0, 'The Night Listener': 3.0, 'Superman Returns': 5.0, 'You, Me and Dupree': 3.5},'Toby': {'Snakes on a Plane':4.5,'You, Me and Dupree':1.0,'Superman Returns':4.0}}

In Python, you can use the pow(n,2)function to square a number and take the square root with the sqrt function:

 

>>from math import sqrt>>sqrt(pow(5-4,2)+pow(4-1,2))

after being improved, we use instead

>>1/(1+sqrt(pow(5-4,2)+pow(4-1,2)))

So the value would always be 0 - 1

 

We add the flowing code to recommendations.py

from math import sqrtdef sim_distance(prefs,person1,person2):    si={}    for item in prefs[person1]:        if item in prefs[person2]:            si[item]=1    if len(si)==0:return 0    sum_of_squares=sum([pow(prefs[person1][item]-prefs[person2][item],2)                        for item in prefs[person1] if item in prefs[person2]])    print(1/(1+sum_of_squares))sim_distance(critics, 'Lisa Rose', 'Claudia Puig')