在列表中创建字典时，在Python代码中丢失元素？ [英] Losing elements in python code while creating a dictionary from a list?

问题描述

 打印length：，len（pub）＃length：420 
 pub_dict = dict（（p.key，p）for p in pub）
 printdict：，len（pub_dict）＃length：163 
  / pre> 
 
 
如果我明白这个权利，我会收到一个包含属性 p.key 作为关键字的字典，对象 p 作为 pub 的每个元素的值。有没有一些副作用我看不到？因为 len（pub_dict）应该与 len（pub）相同，这当然不是在这里，还是我错误？
解决方案
由于您可能有几个p具有相同的密钥，那么您可以使用列表作为新密钥的值：pub_dict = {} pre pre pre pre pre pre pre pre $ p $ 
 pub_dict [p.key] = [] 
 pub_dict [p.key] .append（p）
  

或者如果您需要唯一标识每个记录，您可以使用任何组合键，如键+任何其他p属性值

I have some headache with this python code.

    print "length:", len(pub) # length: 420
    pub_dict = dict((p.key, p) for p in pub)
    print "dict:", len(pub_dict) # length: 163

If I understand this right, I get a dictionary containing the attribute p.key as key and the object p as its value for each element of pub. Are there some side effect I don't see? Because len(pub_dict) should be the same as len(pub) and it is certainly not here, or am I mistaken?

解决方案

Since you may have several p with the same key then you may use list as value for you key within new dicitionary:

pub_dict = {}    
for p in pub:
   if not p.key in pub_dict:
      pub_dict[p.key] = []
   pub_dict[p.key].append(p)

Or if it is neccessary for you to uniquely identify each record you may use any combined key like key + any other p propery value

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