如何使用 Nokogiri 解析 HTML table？

Question

我正在尝试解析 table，但我不知道如何保存其中的数据。我想将每一行中的数据保存为：

['Raw name 1', 2,094, 0,017, 0,098, 0,113, 0,452]

样本table是：

html = <<EOT
    <table class="open">
        <tr>
            <th>Table name</th>
            <th>Column name 1</th>
            <th>Column name 2</th>
            <th>Column name 3</th>
            <th>Column name 4</th>
            <th>Column name 5</th>
        </tr>
        <tr>
            <th>Raw name 1</th>
            <td>2,094</td>
            <td>0,017</td>
            <td>0,098</td>
            <td>0,113</td>
            <td>0,452</td>         
        </tr>
        .
        .
        .
        <tr>
            <th>Raw name 5</th>
            <td>2,094</td>
            <td>0,017</td>
            <td>0,098</td>
            <td>0,113</td>
            <td>0,452</td>         
        </tr>
    </table>
EOT

我的爬虫代码是：

  doc = Nokogiri::HTML(open(html), nil, 'UTF-8')
  tables = doc.css('div.open')

  @tablesArray = []

  tables.each do |table|
    title = table.css('tr[1] > th').text
    cell_data = table.css('tr > td').text
    raw_name = table.css('tr > th').text
    @tablesArray << Table.new(cell_data, raw_name)
  end

  render template: 'scrape_krasecology'
  end
  end

当我尝试在 HTML 页面中显示数据时，看起来所有列名都存储在一个数组的元素中，所有数据都以相同的方式存储。

Answer 1

问题的关键是对多个结果调用 #text 将 return 每个单独元素的 #text 的串联。

让我们检查一下每个步骤的作用：

# Finds all <table>s with class open
# I'm assuming you have only one <table> so
#  you don't actually have to loop through
#  all tables, instead you can just operate
#  on the first one. If that is not the case,
#  you can use a loop the way you did
tables = doc.css('table.open')

# The text of all <th>s in <tr> one in the table
title = table.css('tr[1] > th').text

# The text of all <td>s in all <tr>s in the table
# You obviously wanted just the <td>s in one <tr>
cell_data = table.css('tr > td').text

# The text of all <th>s in all <tr>s in the table
# You obviously wanted just the <th>s in one <tr>
raw_name = table.css('tr > th').text

现在我们知道出了什么问题，下面是一个可能的解决方案：

html = <<EOT
    <table class="open">
        <tr>
            <th>Table name</th>
            <th>Column name 1</th>
            <th>Column name 2</th>
            <th>Column name 3</th>
            <th>Column name 4</th>
            <th>Column name 5</th>
        </tr>
        <tr>
            <th>Raw name 1</th>
            <td>1001</td>
            <td>1002</td>
            <td>1003</td>
            <td>1004</td>
            <td>1005</td>         
        </tr>
        <tr>
            <th>Raw name 2</th>
            <td>2001</td>
            <td>2002</td>
            <td>2003</td>
            <td>2004</td>
            <td>2005</td>         
        </tr>
        <tr>
            <th>Raw name 3</th>
            <td>3001</td>
            <td>3002</td>
            <td>3003</td>
            <td>3004</td>
            <td>3005</td>         
        </tr>
    </table>
EOT

doc = Nokogiri::HTML(html, nil, 'UTF-8')

# Fetches only the first <table>. If you have
#  more than one, you can loop the way you
#  originally did.
table = doc.css('table.open').first

# Fetches all rows (<tr>s)
rows = table.css('tr')

# The column names are the first row (shift returns
#  the first element and removes it from the array).
# On that row we get the text of each individual <th>
# This will be Table name, Column name 1, Column name 2...
column_names = rows.shift.css('th').map(&:text)

# On each of the remaining rows
text_all_rows = rows.map do |row|

  # We get the name (<th>)
  # On the first row this will be Raw name 1
  #  on the second - Raw name 2, etc.
  row_name = row.css('th').text

  # We get the text of each individual value (<td>)
  # On the first row this will be 1001, 1002, 1003...
  #  on the second - 2001, 2002, 2003... etc
  row_values = row.css('td').map(&:text)

  # We map the name, followed by all the values
  [row_name, *row_values]
end

p column_names  # => ["Table name", "Column name 1", "Column name 2",
                #     "Column name 3", "Column name 4", "Column name 5"]
p text_all_rows # => [["Raw name 1", "1001", "1002", "1003", "1004", "1005"],
                #     ["Raw name 2", "2001", "2002", "2003", "2004", "2005"],
                #     ["Raw name 3", "3001", "3002", "3003", "3004", "3005"]]

# If you want to combine them
text_all_rows.each do |row_as_text|
  p column_names.zip(row_as_text).to_h
end # =>
    # {"Table name"=>"Raw name 1", "Column name 1"=>"1001", "Column name 2"=>"1002", "Column name 3"=>"1003", "Column name 4"=>"1004", "Column name 5"=>"1005"}
    # {"Table name"=>"Raw name 2", "Column name 1"=>"2001", "Column name 2"=>"2002", "Column name 3"=>"2003", "Column name 4"=>"2004", "Column name 5"=>"2005"}
    # {"Table name"=>"Raw name 3", "Column name 1"=>"3001", "Column name 2"=>"3002", "Column name 3"=>"3003", "Column name 4"=>"3004", "Column name 5"=>"3005"}

Answer 2

你想要的输出是胡说八道：

['Raw name 1', 2,094, 0,017, 0,098, 0,113, 0,452]
# ~> -:1: Invalid octal digit
# ~> ['Raw name 1', 2,094, 0,017, 0,098, 0,113, 0,452]

我假设你想要引用的数字。

在剥离使代码无法工作的东西并将 HTML 简化为更易于管理的示例之后，然后运行它：

require 'nokogiri'

html = <<EOT
    <table class="open">
        <tr>
            <th>Table name</th>
            <th>Column name 1</th>
            <th>Column name 2</th>
        </tr>
        <tr>
            <th>Raw name 1</th>
            <td>2,094</td>
            <td>0,017</td>
        </tr>
        <tr>
            <th>Raw name 5</th>
            <td>2,094</td>
            <td>0,017</td>
        </tr>
    </table>
EOT


doc = Nokogiri::HTML(html)
tables = doc.css('table.open')

tables_data = []

tables.each do |table|
  title = table.css('tr[1] > th').text # !> assigned but unused variable - title
  cell_data = table.css('tr > td').text
  raw_name = table.css('tr > th').text
  tables_data << [cell_data, raw_name]
end

这导致：

tables_data
# => [["2,0940,0172,0940,017",
#      "Table nameColumn name 1Column name 2Raw name 1Raw name 5"]]

首先要注意的是你没有使用 title 虽然你分配给它。例如，当您清理代码时可能会发生这种情况。

css，像search和xpath，returns一个NodeSet，类似于一个节点数组。当您在 NodeSet 上使用 text 或 inner_text 时，它 returns 每个节点的文本连接成一个字符串：

Get the inner text of all contained Node objects.

这是它的行为：

require 'nokogiri'

doc = Nokogiri::HTML('<html><body><p>foo</p><p>bar</p></body></html>')

doc.css('p').text # => "foobar"

相反，您应该遍历找到的每个节点，并分别提取其文本。这在 SO:

上被覆盖很多次

doc.css('p').map{ |node| node.text } # => ["foo", "bar"]

可以简化为：

doc.css('p').map(&:text) # => ["foo", "bar"]

另见“”。

文档对 content、text 和 inner_text 与节点一起使用时这样说：

Returns the content for this Node.

相反，您需要查找单个节点的文本：

require 'nokogiri'

html = <<EOT
    <table class="open">
        <tr>
            <th>Table name</th>
            <th>Column name 1</th>
            <th>Column name 2</th>
            <th>Column name 3</th>
            <th>Column name 4</th>
            <th>Column name 5</th>
        </tr>
        <tr>
            <th>Raw name 1</th>
            <td>2,094</td>
            <td>0,017</td>
            <td>0,098</td>
            <td>0,113</td>
            <td>0,452</td>         
        </tr>
        <tr>
            <th>Raw name 5</th>
            <td>2,094</td>
            <td>0,017</td>
            <td>0,098</td>
            <td>0,113</td>
            <td>0,452</td>         
        </tr>
    </table>
EOT


tables_data = []

doc = Nokogiri::HTML(html)

doc.css('table.open').each do |table|

  # find all rows in the current table, then iterate over the second all the way to the final one...
  table.css('tr')[1..-1].each do |tr|

    # collect the cell data and raw names from the remaining rows' cells...
    raw_name = tr.at('th').text
    cell_data = tr.css('td').map(&:text)

    # aggregate it...
    tables_data += [raw_name, cell_data]
  end
end

现在的结果是：

tables_data
# => ["Raw name 1",
#     ["2,094", "0,017", "0,098", "0,113", "0,452"],
#     "Raw name 5",
#     ["2,094", "0,017", "0,098", "0,113", "0,452"]]

您可以弄清楚如何将引用的数字强制转换为 Ruby 可接受的小数，或者根据需要操作内部数组。

Answer 3

我假设你是从这里或任何其他相关参考借用了一些代码（或者我很抱歉添加了错误的参考）- http://quabr.com/34781600/ruby-nokogiri-parse-html-table.

但是，如果你想捕获所有的行，你可以更改以下代码 -

希望这能帮助您解决问题。

doc = Nokogiri::HTML(open(html), nil, 'UTF-8')

# We need .open tr, because we want to capture all the columns from a specific table's row

@tablesArray = doc.css('table.open tr').reduce([]) do |array, row|
  # This will allow us to create result as this your illustrated one
  # ie. ['Raw name 1', 2,094, 0,017, 0,098, 0,113, 0,452]
  array << row.css('th, td').map(&:text)
end

render template: 'scrape_krasecology'

如何使用 Nokogiri 解析 HTML table？

How to parse a HTML table with Nokogiri?

ruby

ruby-on-rails

html-parsing

nokogiri