Question

我是Python的新手，遇到了一个我无法解决的问题。

我已将以下解析树从JSON解码为以下列表。

>>> tree
['S', ['NP', ['DET', 'There']], ['S', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', 'asbestos']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]

使用递归函数，我已经能够获得包含终端词的列表。

def explorer(tree):
    for sub in tree[1:]:
        if(type(sub) == str):
            allwords.append(sub)
        else:
            explorer(sub)

>>> allwords
['There', 'is', 'no', 'asbestos', 'in', 'our', 'products', 'no'.]

现在我需要替换原始树中符合某些条件的单词，以便我得到这样的结果：

['S', ['NP', ['DET', 'There']], ['S', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', '_REPLACED_']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]

我尝试了以下功能，但是我无法向上传播替换，所以我总是得到相同的旧原始树。

def replacer(tree):
    string=[]
    for sub in tree[1:]:
        if(type(sub) == str):
            if #'condition is true':
                sub="_REPLACE_"
                return sub
            else: return sub    
        else:
            string.extend(replacer(sub))
    print(string)

我很欣赏一些如何实现结果的提示。提前谢谢。

Answer 1

您的问题是您在某些情况下返回字符串，并在其他情况下打印列表。确保你的替换者总是返回一个字符串列表，你应该没问题。

Answer 2

所以这是一个如何使用列表推导来做这种事情的例子。如果你不知道，列表理解是something = [explorer(x) for x in something]。这也是递归发生的地方。你得到的是一个完全相同的结构列表，但你已经“去过”每个端点，可以检查和替换东西。我做了几次任意替换。

>>> tree = ['S', ['NP', ['DET', 'There']], ['S', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', 'asbestos']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]
>>> def explorer(something):
        if type(something) == list:
            something = [explorer(x) for x in something]
        else:   # You may want to check other conditions here, like if it's a string
            if something == 'asbestos':
                something = 'Oh my'
            if something == 'S':
                something = 'Z'
        return something

>>> explorer(tree)
['Z', ['NP', ['DET', 'There']], ['Z', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', 'Oh my']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]
>>>

我在仔细阅读你的文字后发现了一些东西。你无法“向上传播替换”的原因是因为你的循环结构是这样的：

for x in aList:
    if x = somethingSpecial:
        x = somethingElse

这在Python中不起作用，但这样做：

for i,x in enumerate(aList):
    if x = somethingSpecial:
        aList[i] = somethingElse

现在aList已经修改了你想要的方式。如果你不知道enumerate()做了什么，只需复制/粘贴它：

aList = ['a','b','c']
for i,x in enumerate(aList):
    print(i,x)

Answer 3

如果我理解你的问题，解决问题的一种方法就是这样：

 >>> tree = ['S', ['NP', ['DET', 'There']], ['S', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', 'asbestos']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]
 >>> def replacer(tree):
        for i, sub in enumerate(tree[1:]):
            if type(sub) == str and sub == 'asbestos':
                tree[i+1] = '__REPLACE__'
            else:
                replacer(sub)

如果对树[1：]进行更改，则实际上并未对列表进行更改，而是对拼接进行更改。所以enumerate函数可以解决这个问题。您的sub="_REPLACE_"实际上并未更改列表。它只是为名称sub指定一个新值。

结果：

>>> replacer(tree)
>>> tree
['S', ['NP', ['DET', 'There']], ['S', ['VP', ['VERB', 'is'], ['VP', ['NP', ['DET', 'no'], ['NOUN', '__REPLACE__']], ['VP', ['PP', ['ADP', 'in'], ['NP', ['PRON', 'our'], ['NOUN', 'products']]], ['ADVP', ['ADV', 'now']]]]], ['.', '.']]]

要获得第一个函数创建的新列表，您只需将第一个函数应用于新的tree列表：

>>> explorer(tree)
['There', 'is', 'no', '__REPLACE__', 'in', 'our', 'products', 'now', '.']

python中的JSON，列表和递归

3 个答案: