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- 2-2 ～ 2-3-1 辺り

書籍の通りに実行 ⇒ 失敗

以下のファイルを作る

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}}

実行

$ python
>>> from recommendations import critics
>>> critics['Lisa Rose']['Lady in the Water']
2.5

インタプリタは実行中のまま、ファイルに追記する
- 下記のコードはサンプルのまま

recommendations.py

from math import sqrt

# Returns a distance-based similarity score for person1 and person2
def sim_distance(prefs,person1,person2):
  # Get the list of shared_items
  si={}
  for item in prefs[person1]: 
    if item in prefs[person2]: si[item]=1

  # if they have no ratings in common, return 0
  if len(si)==0: return 0

  # Add up the squares of all the differences
  sum_of_squares=sum([pow(prefs[person1][item]-prefs[person2][item],2) 
                      for item in prefs[person1] if item in prefs[person2]])

  return 1/(1+sum_of_squares)

実行(続き)

>>> reload(recommendations)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'reload' is not defined

できない！！

解決

解決までの流れ

誤記が多いらしい → 正誤表より import recommendationsしてみる

>>> import recommendations
>>> reload(recommendations)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'reload' is not defined

書籍はpython 2.4.1 → 実行環境は3.6.5
- #importlib.reload
- モジュールのリロード

>>> import importlib
>>> importlib.reload(recommendations)
<module 'recommendations' from '/hoge/recommendations.py'>
>>> recommendations.sim_distance(recommendations.critics,'Lisa Rose','Gene Seymour')
0.14814814814814814

できた！

結局どうすれば良かったか

>>> import recommendations
>>> import importlib
>>> importlib.reload(recommendations)
<module 'recommendations' from '/hoge/recommendations.py'>
>>> recommendations.sim_distance(recommendations.critics,'Lisa Rose','Gene Seymour')
0.14814814814814814

参考

O'Reilly 集合知プログラミング
- 正誤表
- サンプルプログラム