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。

我需要将术语附加到列表的空列表中。我从：

开始

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

我想以

结束

Talks[eachFilename][SomeTermsRemoved]=
      [['paragraph','text'],
       ['paragraph','2'],
       ['paragraph']]

Talks[eachFilename][SomeTermsRemoved]开始为空。我无法指定我想要的内容：

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

等......（IndexError：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，我得到一个字符串是不可变的错误。

那么，如何指定我希望Talks[eachFilename][SomeTermsRemoved][0]为['paragraph','text']，Talks[eachFilename][SomeTermsRemoved][1]为['paragraph','2']等？

.append有效，但只生成一个长列，而不是一组列表。

更具体地说，我有一些在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有几行长文本（单个段落）

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

TermVectors由NLTK包填充，其中包含一系列术语，仍然在原始段落中分组：

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

我想进一步操纵TermVectors，但保留原始段落列表结构。这将创建一个每行包含1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（我丢失了段落结构）：

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

Answer 1

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填充了字符串，否则没有任何意义。无论如何，如果你从一个空列表开始，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分配给它，则会抛出错误：

>>> empty_list = []
>>> empty_list[0] = 10
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range

顺便说一句，这样的代码：

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风格相差甚远。不要使用 camelCase ，请使用 snake_case 。不要把变量大都化。此外，在您的中级for循环中，您使用for eachTerm in range(0, len(Talks[eachFilename]['TermVectors']，但eachTerm是int，因此使用标准i {{1}更有意义}或j。甚至k。

无论如何，没有理由为什么代码应该改变这个：

idx

进入这个：

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

这是一个可重复的例子（我已经为你做了这件事，但你在发布一个问题之前应该自己做这件事）：

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

更多的pythonic方法将如下所示：

>>> 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']]}}
>>>

Answer 2

一些持续的实验，以及评论让我走向解决方案。我没有附加生成单个长列表的每个单独的术语，而是将这些术语累积到一个列表中，然后附加每个列表，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！

向空嵌套列表添加新值

2 个答案: