Python字典没有按顺序排列

Question

我创建了一个字母表的字典，其值从 0 开始，并根据 word 文件增加一定数量。我对初始字典进行了硬编码，我希望它保持按字母顺序排列，但它根本没有。我希望它按字母顺序返回字典，基本上与初始字典保持相同。

我怎样才能保持秩序？

from wordData import*

def letterFreq(words):
    
    totalLetters = 0
    letterDict = {'a':0,'b':0,'c':0,'d':0,'e':0,'f':0,'g':0,'h':0,'i':0,'j':0,'k':0,'l':0,'m':0,'n':0,'o':0,'p':0,'q':0,
                  'r':0,'s':0,'t':0,'u':0,'v':0,'w':0,'x':0,'y':0,'z':0}

    for word in words:
        totalLetters += totalOccurences(word,words)*len(word)
        for char in range(0,len(word)):
            for letter in letterDict:
                if letter == word[char]:
                    for year in words[word]:
                        letterDict[letter] += year.count
    for letters in letterDict:
        letterDict[letters] = float(letterDict[letters] / totalLetters)
    print(letterDict)
    return letterDict

def main():
   
    filename = input("Enter filename: ")
    words = readWordFile(filename)
    letterFreq(words)


if __name__ == '__main__':
    main()

Answer 1

Python 3.7+ 更新:

现在有词典 officially maintain insertion order适用于 Python 3.7 及更高版本。

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Python 3.6 更新:

字典在 Python 3.6 中维护插入顺序，但是，this is considered an implementation detail and should not be relied upon .

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原始答案 - 直到并包括 Python 3.5:

字典没有排序，也不会为您保留任何顺序。

您可以使用有序字典，它维护插入顺序:

from collections import OrderedDict
letterDict = OrderedDict([('a', 0), ('b', 0), ('c', 0)])

或者您可以只返回字典内容的排序列表

letterDict = {'a':0,'b':0,'c':0}
sortedList = sorted([(k, v) for k, v in letterDict.iteritems()])

print sortedList # [('a', 0), ('b', 0), ('c', 0)]