將項目分配給對象字典

Question

以下代碼不起作用。

def set_view_counts(self): 
    """ 
    Initializes the view counts for all of the Concept objects in the ConceptModel. See Concept for a 
    description of why this parameter is optional. 
    """ 
    for node in self.nodes(): 
     p = PageviewsClient().article_views("en.wikipedia", [node.concept.replace(' ', '_')]) 
     p = [p[key][node.concept.replace(' ', '_')] for key in p.keys()] 
     p = int(sum([daily_view_count for daily_view_count in p if daily_view_count])/len(p)) 
     node.properties['view_count'] = p 

當我檢查我的node.properties詞典的內容，我覺得4560, 4560, 4560, 4560。

下面的代碼可以。

def set_view_counts(self): 
    """ 
    Initializes the view counts for all of the Concept objects in the ConceptModel. See Concept for a 
    description of why this parameter is optional. 
    """ 
    for node in self.nodes(): 
     p = PageviewsClient().article_views("en.wikipedia", [node.concept.replace(' ', '_')]) 
     p = [p[key][node.concept.replace(' ', '_')] for key in p.keys()] 
     p = int(sum([daily_view_count for daily_view_count in p if daily_view_count])/len(p)) 
     node.properties = p 

當我檢查屬性時，我發現11252, 7367, 3337, 4560。

這是怎麼回事？

Answer 1

我們需要看到更多的代碼，但是我把一些肉在你的功能，猜測你可以寫重現你的錯誤：

class Node: 
    def __init__(self, props={}): 
     self.properties = props 

class G: 
    def __init__(self): 
     self.n = [Node(), Node(), Node(), Node()] 

    def nodes(self): 
     return self.n 

    def set_view_counts(self): 
     p = 0 
     for node in self.nodes(): 
      node.properties['view_count'] = p 
      p = p + 1 

    def __repr__(self): 
     r = '' 
     for node in self.nodes(): 
      r += node.properties.__repr__() 
     return r 

g = G() 
g.set_view_counts() 
print g 

有了這個，我得到：

{'view_count': 3}{'view_count': 3}{'view_count': 3}{'view_count': 3} 

這是因爲Node.__init__中props參數的默認值。所有Nodes共享相同的dict（用作默認值的那個）。通過刪除默認值來解決這個問題。