Python：嵌套iteritems循環只能運行一次

Question

我想循環一個字典，並在其中添加字典。但是當我使用循環使用iteritems（）時，它只是迭代一次並退出到外部循環。我在Python中很新，但我認爲這個代碼應該工作。

爲什麼會發生這種情況？

from __future__ import division 
import numpy 
import pprint 

training = {"outlook":{"sunny":{"yes":2,"no":3},"overcast":{"yes":4,"no":0},"rainy":{"yes":3,"no":2}},\ 
      "temperature":{"yes":[83,70,68,64,69,75,75,72,81],"no":[85,80,65,72,71]},\ 
      "humidity":{"yes":[86,96,80,65,70,80,70,90,75],"no":[85,90,70,95,91]},\ 
      "windy":{"false":{"yes":6,"no":2},"true":{"yes":3,"no":3}},\ 
      "play":{"yes":9,"no":5}} 
processed = {} 
total_yes = training["play"]["yes"] 
total_no = training["play"]["no"] 
total_all = training["play"]["no"]+training["play"]["yes"] 

def main(): 
    for k,v in training.iteritems(): 
     if(k != "play"): 
      for k2,v2 in v.iteritems(): 
       if((k2 == "yes") & isinstance(v2,list)): 
        processed[k] = {"yes":{"mean":numpy.mean(v2),"std":numpy.std(v2,ddof=1)}} 
       elif((k2 == "no") & isinstance(v2,list)): 
        processed[k].update({"no":{"mean":numpy.mean(v2),"std":numpy.std(v2,ddof=1)}}) 
       else: 
        processed[k] = {} 

        # the problems start here 
        for i,j in v2.iteritems(): 
         if(i == "yes"): 
          p_yes = j/total_yes 
          processed[k].update({k2:{"yes":p_yes,"no":(1-p_yes)}}) 
         #when I print processed[k], it contains current value only (not including previous value) 
       #suddenly exit after iterating once 

     else: 
      processed[k] = {"yes":total_yes/total_all,"no":total_no/total_all} 

    pp = pprint.PrettyPrinter(indent=3) 
    pp.pprint(processed) 

if __name__ == '__main__': 
    main() 

輸出是：

... 
'outlook': { 'sunny': { 'no': 0.7777777777777778, 
          'yes': 0.2222222222222222}}, 
... 

但預期輸出是：

... 
'outlook': { 'sunny': { 'no': 0.7777777777777778, 
          'yes': 0.2222222222222222}}, 
       'overcast': { 'no':xxxxx, 
          'yes':xxx 
          } 
       ... 
... 

Answer 1

你的錯誤是，你總是刪除「前景」，到最後你看到的插入到'outlook'字典中的最後一個條目。這裏是你的代碼的修復：

from __future__ import division 
import numpy 
import pprint 

training = {"outlook":{"sunny":{"yes":2,"no":3},"overcast":{"yes":4,"no":0},"rainy":{"yes":3,"no":2}},\ 
     "temperature":{"yes":[83,70,68,64,69,75,75,72,81],"no":[85,80,65,72,71]},\ 
     "humidity":{"yes":[86,96,80,65,70,80,70,90,75],"no":[85,90,70,95,91]},\ 
     "windy":{"false":{"yes":6,"no":2},"true":{"yes":3,"no":3}},\ 
     "play":{"yes":9,"no":5}} 
processed = {} 
total_yes = training["play"]["yes"] 
total_no = training["play"]["no"] 
total_all = training["play"]["no"]+training["play"]["yes"] 


def main(): 
    for k,v in training.iteritems(): 
     if (k=='outlook'): 
      pass 
     if(k != "play"): 
      for k2,v2 in v.iteritems(): 
       if((k2 == "yes") & isinstance(v2,list)): 
        processed[k] = {"yes":{"mean":numpy.mean(v2),"std":numpy.std(v2,ddof=1)}} 
       elif((k2 == "no") & isinstance(v2,list)): 
        processed[k].update({"no":{"mean":numpy.mean(v2),"std":numpy.std(v2,ddof=1)}}) 
       else: 
        if k not in processed: 
         processed[k] = {} 

        for i,j in v2.iteritems(): 
         if(i == "yes"): 
          p_yes = j/total_yes 
          processed[k].update({k2:{"yes":p_yes,"no":(1-p_yes)}})      


     else: 
      processed[k] = {"yes":total_yes/total_all,"no":total_no/total_all} 

    pp = pprint.PrettyPrinter(indent=3) 
    pp.pprint(processed) 

if __name__ == '__main__': 
    main() 

Answer 2

的問題就在這裏：

else: 
    processed[k] = {} 

k的前值被改寫爲您的for循環移動到下一個元素。

這裏定義這一點，你的問題應該得到解決：

for k,v in training.iteritems(): 
    if(k != "play"): 
     processed[k] = {}