4

我正在尝试根据停用词列表将 Ruby 中的字符串拆分为更小的子字符串或短语。split 方法在我直接定义正则表达式模式时起作用;但是,当我尝试通过在 split 方法本身内进行评估来定义模式时,它不起作用。

在实践中,我想阅读停用词的外部文件并用它来拆分我的句子。所以,我希望能够从外部文件构造模式,而不是直接指定它。我还注意到,当我使用“pp”和“puts”时,我的行为非常不同,我不知道为什么。我在 Windows 上使用 Ruby 2.0 和 Notepad++。

 require 'pp'
 str = "The force be with you."     
 pp str.split(/(?:\bthe\b|\bwith\b)/i)
 => ["", " force be ", " you."]
 pp str.split(/(?:\bthe\b|\bwith\b)/i).collect(&:strip).reject(&:empty?)
 => ["force be", "you."] 

上面的最终数组是我想要的结果。但是,这在下面不起作用:

 require 'pp'
 stop_array = ["the", "with"]
 str = "The force be with you." 
 pattern = "(?:" + stop_array.map{|i| "\b#{i}\b" }.join("|") + ")"
 puts pattern
 => (?thwit)
 puts str.split(/#{pattern}/i)
 => The force be with you.
 pp pattern
 => "(?:\bthe\b|\bwith\b)"
 pp str.split(/#{pattern}/i)
 => ["The force be with you."]

更新:使用下面的评论,我修改了我的原始脚本。我还创建了一种拆分字符串的方法。

 require 'pp'

 class String
      def splitstop(stopwords=[])
      stopwords_regex = /\b(?:#{ Regexp.union(*stopwords).source })\b/i
      return split(stopwords_regex).collect(&:strip).reject(&:empty?)
      end
 end

 stop_array = ["the", "with", "over"]

 pp "The force be with you.".splitstop stop_array
 => ["force be", "you."]
 pp "The quick brown fox jumps over the lazy dog.".splitstop stop_array
 => ["quick brown fox jumps", "lazy dog."]
4

4 回答 4

4

我会这样做:

str = "The force be with you."     
stop_array = %w[the with]
stopwords_regex = /(?:#{ Regexp.union(stop_array).source })/i
str.split(stopwords_regex).map(&:strip) # => ["", "force be", "you."]

使用时Regexp.union,注意生成的实际模式很重要:

/(?:#{ Regexp.union(stop_array) })/i
=> /(?:(?-mix:the|with))/i

嵌入式(?-mix:会关闭模式内不区分大小写的标志,这可能会破坏模式,导致它抓取错误的东西。相反,您必须告诉引擎只返回模式,而不返回标志:

/(?:#{ Regexp.union(stop_array).source })/i
=> /(?:the|with)/i

这就是为什么pattern = "(?:\bthe\b|\bwith\b)"不起作用:

/#{pattern}/i # => /(?:\x08the\x08|\x08with\x08)/i

Ruby 将"\b"其视为退格字符。而是使用:

pattern = "(?:\\bthe\\b|\\bwith\\b)"
/#{pattern}/i # => /(?:\bthe\b|\bwith\b)/i
于 2013-06-12T07:32:02.063 回答
0

你必须掩盖反斜杠:

"\\b#{i}\\b" 

IE

pattern = "(?:" + stop_array.map{|i| "\\b#{i}\\b" }.join("|") + ")"

和一个小的改进/简化:

pattern = "\\b(?:" + stop_array.join("|") + ")\\b"

然后:

str.split(/#{pattern}/i) # => ["", " force be ", " you."]

如果您的停止清单很短,我认为这是正确的方法。

于 2013-06-12T06:59:16.517 回答
0
stop_array = ["the", "with"]
re = Regexp.union(stop_array.map{|w| /\s*\b#{Regexp.escape(w)}\b\s*/i})

"The force be with you.".split(re) # =>
[
  "",
  "force be",
  "you."
]
于 2013-06-12T07:06:10.387 回答
0
s = "the force be with you."
stop_words = %w|the with is|
# dynamically create a case-insensitive regexp
regexp = Regexp.new stop_words.join('|'), true
result = []
while(match = regexp.match(s))
  word = match.pre_match unless match.pre_match.empty?
  result << word
  s = match.post_match
end
# the last unmatched content, if any
result << s
result.compact!.map(&:strip!)

pp result
=> ["force be", "you."]
于 2013-06-12T10:21:03.987 回答