# 基于用户的协同过滤算法

```import random
import math
class UserBasedCF:
def __init__(self,datafile = None):
self.datafile = datafile
self.splitData(3,47)
"""
read the data from the data file which is a data set
"""
self.datafile = datafile or self.datafile
self.data = []
for line in open(self.datafile):
userid,itemid,record,_ = line.split()
self.data.append((userid,itemid,int(record)))
def splitData(self,k,seed,data=None,M = 8):
"""
split the data set
testdata is a test data set
traindata is a train set
test data set / train data set is 1:M-1
"""
self.testdata = {}
self.traindata = {}
data = data or self.data
random.seed(seed)
for user,item, record in self.data:
if random.randint(0,M) == k:
self.testdata.setdefault(user,{})
self.testdata[user][item] = record
else:
self.traindata.setdefault(user,{})
self.traindata[user][item] = record
def userSimilarity(self,train = None):
"""
One method of getting user similarity matrix
"""
train = train or self.traindata
self.userSim = dict()
for u in train.keys():
for v in train.keys():
if u == v:
continue
self.userSim.setdefault(u,{})
self.userSim[u][v] = len(set(train[u].keys()) & set(train[v].keys()))
self.userSim[u][v] /=math.sqrt(len(train[u]) * len(train[v]) *1.0)
def userSimilarityBest(self,train = None):
"""
the other method of getting user similarity which is better than above
you can get the method on page 46
In this experiment，we use this method
"""
train = train or self.traindata
self.userSimBest = dict()
item_users = dict()
for u,item in train.items():
for i in item.keys():
item_users.setdefault(i,set())
user_item_count = dict()
count = dict()
for item,users in item_users.items():
for u in users:
user_item_count.setdefault(u,0)
user_item_count[u] += 1
for v in users:
if u == v:continue
count.setdefault(u,{})
count[u].setdefault(v,0)
count[u][v] += 1
for u ,related_users in count.items():
self.userSimBest.setdefault(u,dict())
for v, cuv in related_users.items():
self.userSimBest[u][v] = cuv / math.sqrt(user_item_count[u] * user_item_count[v] * 1.0)

def recommend(self,user,train = None,k = 8,nitem = 40):
train = train or self.traindata
rank = dict()
interacted_items = train.get(user,{})
for v ,wuv in sorted(self.userSimBest[user].items(),key = lambda x : x[1],reverse = True)[0:k]:
for i , rvi in train[v].items():
if i in interacted_items:
continue
rank.setdefault(i,0)
rank[i] += wuv
return dict(sorted(rank.items(),key = lambda x :x[1],reverse = True)[0:nitem])
def recallAndPrecision(self,train = None,test = None,k = 8,nitem = 10):
"""
Get the recall and precision, the method you want to know is listed
in the page 43
"""
train  = train or self.traindata
test = test or self.testdata
hit = 0
recall = 0
precision = 0
for user in train.keys():
tu = test.get(user,{})
rank = self.recommend(user, train = train,k = k,nitem = nitem)
for item,_ in rank.items():
if item in tu:
hit += 1
recall += len(tu)
precision += nitem
return (hit / (recall * 1.0),hit / (precision * 1.0))
def coverage(self,train = None,test = None,k = 8,nitem = 10):
train = train or self.traindata
test = test or self.testdata
recommend_items = set()
all_items  = set()
for user in train.keys():
for item in train[user].keys():
rank = self.recommend(user, train, k = k, nitem = nitem)
for item,_ in rank.items():
return len(recommend_items) / (len(all_items) * 1.0)
def popularity(self,train = None,test = None,k = 8,nitem = 10):
"""
Get the popularity
the algorithm on page 44
"""
train = train or self.traindata
test = test or self.testdata
item_popularity = dict()
for user ,items in train.items():
for item in items.keys():
item_popularity.setdefault(item,0)
item_popularity[item] += 1
ret = 0
n = 0
for user in train.keys():
rank = self.recommend(user, train, k = k, nitem = nitem)
for item ,_ in rank.items():
ret += math.log(1+item_popularity[item])
n += 1
return ret / (n * 1.0)

def testRecommend():
ubcf = UserBasedCF('u.data')
ubcf.splitData(4,100)
ubcf.userSimilarity()
user = "345"
rank = ubcf.recommend(user,k = 3)
for i,rvi in rank.items():

items = ubcf.testdata.get(user,{})
record = items.get(i,0)
print "%5s: %.4f--%.4f" %(i,rvi,record)
def testUserBasedCF():
cf  =  UserBasedCF('u.data')
cf.userSimilarityBest()
print "%3s%20s%20s%20s%20s" % ('K',"recall",'precision','coverage','popularity')
for k in [5,10,20,40,80,160]:
recall,precision = cf.recallAndPrecision( k = k)
coverage = cf.coverage(k = k)
popularity = cf.popularity(k = k)
print "%3d%19.3f%%%19.3f%%%19.3f%%%20.3f" % (k,recall * 100,precision * 100,coverage * 100,popularity)

if __name__ == "__main__":
testUserBasedCF()
#该片段来自于http://outofmemory.cn
```

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