[英]AttributeError: 'dict' object has no attribute 'predictors'
我是 python 新手,找不到答案。 參考消息末尾的代碼,我能知道下一行中的“for item, total in totals.items()”部分是什么意思嗎?
rankings = [(total/simSums[item], item) for item, total in totals.items()]
另外,代碼失敗並說
AttributeError: 'dict' 對象沒有屬性 'predictors'
當我將代碼中“item(s)”的所有實例更改為“predictor(s)”時。 為什么呢?
# Return the Pearson correlation coefficient for p1 and p2
def sim_person(prefs, p1, p2):
# Get the list of shared_items
si={}
for item in prefs[p1]:
if item in prefs[p2]:si[item]=1
# Find the number of elements
n=len(si)
# if they have no ratings in common, return 0
if n==0: return 0
# Add up all the preferences
sum1 = sum([prefs[p1][it] for it in si])
sum2 = sum([prefs[p2][it] for it in si])
# Sum up the squares
sum1Sq = sum([pow(prefs[p1][it],2) for it in si])
sum2Sq = sum([pow(prefs[p2][it],2) for it in si])
# Sum up the products
pSum = sum([prefs[p1][it]*prefs[p2][it] for it in si])
# Calculate Person score
num = pSum - (sum1*sum2/n)
den = sqrt((sum1Sq - pow(sum1,2)/n)*(sum2Sq - pow(sum2,2)/n))
if den == 0: return 0
r = num/den
return r
# Returns the best matches for person from the prefs dictionary.
# Number of results and similarity function are optional params.
def topMatch(prefs, person, n=5, similarity=sim_person):
scores = [(similarity(prefs, person, other), other)
for other in prefs if other!=person]
# Sort the list so the highest scores appear at the top
scores.sort()
scores.reverse()
return scores[0:n]
# Gets recommendations for a person by using a weighted average
# of every other user's rankings
def getRecommendations(prefs, person, similarity=sim_person):
totals = {}
simSums = {}
for other in prefs:
# don't compare me to myself
if other == person: continue
sim = similarity(prefs, person, other)
# ignore scores of zero of lower
if sim<=0: continue
for item in prefs[other]:
# only score movies I haven't seen yet
if item not in prefs[person] or prefs[person][item]==0:
# Similarity * Score
totals.setdefault(item, 0)
totals[item]+=prefs[other][item]*sim
# Sum of similarities
simSums.setdefault(item, 0)
simSums[item]+=sim
# Create the normalized list
rankings = [(total/simSums[item], item) for item, total in totals.items()]
# Return the sorted list
rankings.sort()
rankings.reverse()
return rankings
dict.items
迭代字典的鍵值對。 因此, for key, value in dictionary.items()
將遍歷每一對。 這是文檔信息,您可以在官方網頁中查看,或者更簡單,打開 python 控制台並鍵入help(dict.items)
。 現在,舉個例子:
>>> d = {'hello': 34, 'world': 2999}
>>> for key, value in d.items():
... print key, value
...
world 2999
hello 34
AttributeError
是當對象不具有您嘗試訪問的屬性時拋出的異常。 類dict
沒有任何predictors
屬性(現在您知道在哪里檢查它:)),因此當您嘗試訪問它時它會抱怨。 就這么簡單。
#Try without dot notation sample_dict = {'name': 'John', 'age': 29} print(sample_dict['name']) # John print(sample_dict['age']) # 29
product_details = {
'name':'mobile',
'company':'samsung'}
訪問 product_details.name 將拋出錯誤“dict object has no attribute 'name'”。 原因是因為我們使用點 (.) 來訪問 dict 項目。
right way is :
product_details['name']
我們使用點運算符從 python 中的對象訪問值。
dictionary.items() 允許我們遍歷字典中的鍵:值對
for key, value in product_details.items():
print(key,':',value)
對於循環的每次迭代,一個鍵和它的值被分配給這里的變量鍵和值。 這就是 items() 方法的工作原理。
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