向空嵌套列表添加新值

Question

这与How to append to the end of an empty list?有关，但我还没有足够的声誉在那里发表评论，所以我在这里发布了一个新问题。在

我需要在一个空的列表中添加术语。我从以下几点开始：

Talks[eachFilename][TermVectors]=
      [['paragraph','1','text'],
       ['paragraph','2','text'],
       ['paragraph','3','text']]

我想以

^{pr2}$

Talks[eachFilename][SomeTermsRemoved]开始为空。我不能指定我想要：

Talks[eachFilename][SomeTermsRemoved][0][0]='paragraph'
Talks[eachFilename][SomeTermsRemoved][0][1]='text'
Talks[eachFilename][SomeTermsRemoved][1][0]='paragraph'

等等。。。（索引器错误：列表索引超出范围）。如果我强制填充字符串，然后尝试更改它，就会得到一个字符串是不可变错误的。在

那么，如何指定我希望Talks[eachFilename][SomeTermsRemoved][0]是['paragraph','text']，而{}是{}等等？在

.append可以工作，但只生成一个长列，而不是一组列表。在

更具体地说，我有许多在dict中初始化的列表

Talks = {}
Talks[eachFilename]= {}
Talks[eachFilename]['StartingText']=[]
Talks[eachFilename]['TermVectors']=[]
Talks[eachFilename]['TermVectorsNoStops']=[]

eachFilename从文本文件列表中填充，例如：

Talks[eachFilename]=['filename1','filename2']

StartingText有几行很长的文本（单个段落）

Talks[filename1][StartingText]=['This is paragraph one','paragraph two']

术语向量由NLTK包填充，其中包含一个术语列表，仍然分组在原始段落中：

Talks[filename1][TermVectors]=
     [['This','is','paragraph','one'],
      ['paragraph','two']]

我想进一步操作TermVectors，但保留原来的段落列表结构。这将创建一个每行包含一个术语的列表：

for eachFilename in Talks:
    for eachTerm in range( 0, len( Talks[eachFilename]['TermVectors'] ) ):
        for term in Talks[eachFilename]['TermVectors'][ eachTerm ]:
            if unicode(term) not in stop_words:
                Talks[eachFilename]['TermVectorsNoStops'].append( term )

结果（我失去段落结构）：

Talks[filename1][TermVectorsNoStops]=
     [['This'],
      ['is'],
      ['paragraph'],
      ['one'],
      ['paragraph'],
      ['two']]

Answer 1

一些持续的实验，加上这些评论，让我朝着一个解决方案前进。我没有附加每个单独的术语（生成一个长列表），而是将这些术语累积到一个列表中，然后将每个列表追加，如下所示：

for eachFilename in Talks:
    for eachTerm in range( 0, len( Talks[eachFilename]['TermVectors'] ) ):
        term_list = [ ]
        for term in Talks[eachFilename]['TermVectors'][ eachTerm ]:
            if unicode(term) not in stop_words:
                term_list.append(term)
        Talks[eachFilename]['TermVectorsNoStops'].append( term )

谢谢大家！在

Answer 2

您报告的错误（字符串不可变？）除非您的列表实际上不是空的，但已经用字符串填充，否则就没有任何意义。在任何情况下，如果您从一个空列表开始，那么填充它的最简单方法是附加：

>>> talks = {}
>>> talks['each_file_name'] = {}
>>> talks['each_file_name']['terms_removed'] = []
>>> talks['each_file_name']['terms_removed'].append(['paragraph','text'])
>>> talks['each_file_name']['terms_removed'].append(['paragraph','2'])
>>> talks['each_file_name']['terms_removed'].append(['paragraph'])
>>> talks
{'each_file_name': {'terms_removed': [['paragraph', 'text'], ['paragraph', '2'], ['paragraph']]}}
>>> from pprint import pprint
>>> pprint(talks)
{'each_file_name': {'terms_removed': [['paragraph', 'text'],
                                      ['paragraph', '2'],
                                      ['paragraph']]}}

如果您有一个空列表，并尝试使用索引为其分配，则会引发错误：

^{pr2}$

另外，代码如下：

for eachFilename in Talks:
    for eachTerm in range( 0, len( Talks[eachFilename]['TermVectors'] ) ):
        for term in Talks[eachFilename]['TermVectors'][ eachTerm ]:
            if unicode(term) not in stop_words:
                Talks[eachFilename]['TermVectorsNoStops'].append( term )

与Python风格相去甚远。不要使用camelCase，使用snake_case。不要将变量大写。另外，在中级for循环中，使用for eachTerm in range(0, len(Talks[eachFilename]['TermVectors']，但是eachTerm是int，因此使用标准ij或{}。偶数idx。在

无论如何，没有理由让代码变成这样：

Talks[filename1][TermVectors] =
     [['This','is','paragraph','one'],
      ['paragraph','two']] 

在这方面：

Talks[filename1][TermVectors] =
     [['This'],
      ['is'],
      ['paragraph'],
      ['one'],
      ['paragraph'],
      ['two']]

下面是一个可复制的例子（我为您做了这个，但是您应该在发布问题之前自己做）：

>>> pprint(talks)
{'file1': {'no_stops': [],
           'term_vectors': [['This', 'is', 'paragraph', 'one'],
                            ['paragraph', 'two']]},
 'file2': {'no_stops': [],
           'term_vectors': [['This', 'is', 'paragraph', 'three'],
                            ['paragraph', 'four']]}}
>>> for file in talks:
...   for i in range(len(talks[file]['term_vectors'])):
...     for term in talks[file]['term_vectors'][i]:
...       if term not in stop_words:
...         talks[file]['no_stops'].append(term)
... 
>>> pprint(file)
'file2'
>>> pprint(talks)
{'file1': {'no_stops': ['This', 'paragraph', 'one', 'paragraph'],
           'term_vectors': [['This', 'is', 'paragraph', 'one'],
                            ['paragraph', 'two']]},
 'file2': {'no_stops': ['This', 'paragraph', 'paragraph', 'four'],
           'term_vectors': [['This', 'is', 'paragraph', 'three'],
                            ['paragraph', 'four']]}}
>>> 

更像Python的方法如下：

>>> pprint(talks)
{'file1': {'no_stops': [],
           'term_vectors': [['This', 'is', 'paragraph', 'one'],
                            ['paragraph', 'two']]},
 'file2': {'no_stops': [],
           'term_vectors': [['This', 'is', 'paragraph', 'three'],
                            ['paragraph', 'four']]}}
>>> for file in talks.values():
...   file['no_stops'] = [[term for term in sub if term not in stop_words] for sub in file['term_vectors']]
... 
>>> pprint(talks)
{'file1': {'no_stops': [['This', 'paragraph', 'one'], ['paragraph']],
           'term_vectors': [['This', 'is', 'paragraph', 'one'],
                            ['paragraph', 'two']]},
 'file2': {'no_stops': [['This', 'paragraph'], ['paragraph', 'four']],
           'term_vectors': [['This', 'is', 'paragraph', 'three'],
                            ['paragraph', 'four']]}}
>>>