Python:深入追加字典？ - 在一个表达式中

Question

如何在单个表达式中获取一个字典,其中一个键值对已添加到某个输入字典中的子字典中？输入字典应保持不变.可以假设子字典确实存在并且新的键值对不在子字典中.

更新2(见下文"SOsurvivalConditions"的定义等):

最简洁的方法是:

(SOsurvivalConditions['firstCondition'].setdefault('synonym', 'A modern form of RTFM is: Google It.'), SOsurvivalConditions)[-1]

更新1:

这符合给定的要求,没有修改输入字典的副作用:

dict((k,dict(v, synonym='A modern form of RTFM is: Google It.') if k == "firstCondition" else v) for k,v in SOsurvivalConditions.iteritems())

但是,更简洁(但仅限于语句)的方式可以使用辅助函数进行调整,例如:

import copy
def dictDeepAdd(inputDict, dictKey, newKey, newValue):
    """
      Adds new key-value pair to a sub-dictionary and
      returns a new version of inputDict.

      dictKey is the key in inputDict for which a new
      key-value pair is added.

      Side-effect: none (does not change inputDict).
    """
    toReturn = copy.deepcopy(inputDict)
    toReturn[dictKey][newKey] = newValue
    return toReturn

dictDeepAdd(
                 SOsurvivalConditions,
                 'firstCondition',
                 'synonym',
                 'A modern form of RTFM is: Google It.'
           )

---

这个例子:

goodStyle = \
{
    'answer': 'RTFM responses are not acceptable on Stack Overflow - Joel Spolsky has repeatedly said so in the Stack Overflow podcasts.',
    'RTFM'  : 'RTFM is, in the less offensive version, an abbreviation for Read The Fine Manual.',
}

SOsurvivalConditions = \
{
    'moodImperative' : 'be happy',
    'firstCondition' : goodStyle,
}

SOsurvivalConditions中的'firstCondition'现在有两个键值对.需要附加新的键值对("同义词","现代形式的RTFM:Google It."),并且结果应该在单个表达式中可用.

这工作(一行,但在这里分成几个):

{
    'moodImperative': SOsurvivalConditions['moodImperative'],
    'firstCondition' :
        dict(
               SOsurvivalConditions['firstCondition'],
               synonym = 'A modern form of RTFM is: Google It.'
            )
}

并返回:

{'moodImperative': 'be happy', 
 'firstCondition': 
        {'answer': 'RTFM responses are not acceptable on Stack Overflow - Joel Spolsky has repeatedly said so in the Stack Overflow podcasts.', 
         'RTFM': 'RTFM is, in the less offensive version, an abbreviation for Read The Fine Manual.', 
         'synonym': 'A modern form of RTFM is: Google It.'
        }
 }

但是,此表达式中存在大量冗余 - 所有键都重复出现.'firstCondition'出现两次.有更优雅的方式吗？

(这里的数据结构的名称和内容是组成的,但代表了我今天遇到的一个真正的问题.Python版本:2.6.2.).

Answer 1

SOsurvivalConditions['firstCondition']['synonym'] = 'A modern form of RTM is: Google It.'