Python內聯if語句

有人可以幫我使用下面的語法，或者告訴我它是否可行嗎？因爲我要修改if ... else ...條件。我不想在列表中添加重複的值，但我得到了KeyError。Python內聯if語句

其實，我不熟悉這樣的語句：

twins[value] = twins[value] + [box] if value in twins else [box]

是什麼恰恰意味着？

示例代碼

#dictionary 
twins = dict()     
#iterate unitlist 
for unit in unitlist:            
    #finding each twin in the unit 
    for box in unit:        
     value = values[box]        
     if len(value) == 2: 
      twins[value] = twins[value] + [box] if value in twins else [box]

我改性條件

#dictionary 
twins = dict()     
#iterate unitlist 
for unit in unitlist:            
    #finding each twin in the unit 
    for box in unit:        
     value = values[box]        
     if len(value) == 2:        
      if value not in twins:      
       twins[value] = twins[value] + [box]

來源

2017-05-27 KDB

這

twins[value] = twins[value] + [box] if value in twins else [box]

在功能上等效於這樣的：

if value in twins: 
    tmp = twins[value] + [box] 
else: 
    tmp = [box] 
twins[value] = tmp

來源

2017-05-27 09:41:10 freakish

實際上，「雙胞胎[價值] = tmp」應放在if-else內。謝謝 – KDB

您需要使用：

if value in twins:      
    twins[value] = twins[value] + [box] 
else: 
    twins[value] = [box]

，或者如果你想保持你的not in條件：

if value not in twins: 
    twins[value] = [box]    
else:  
    twins[value] = twins[value] + [box]

但你也可以使用dict.get用默認這樣做沒有if完全地：

twins[value] = twins.get(value, []) + [box]

來源

2017-05-27 09:50:14 MSeifert

Python內聯if語句

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