如何在正则表达式中匹配单双 html 属性？

Question

我有一个包含两个不同类的 html 元素。但在某些情况下，我只有一堂课。当有两个类时，它们用空格分隔。

"rating-inbtn hide-if-zero-113"
 or 
"rating-inbtn"

如何在正则表达式中匹配这两种模式。

作为参考，我想放一篇我的旧帖子：

<span class="vote-actions">
    <a class="btn btn-default vote-action-good">
        <span class="icon thumb-up black black-hover">&nbsp;</span>
        <span class="rating-inbtn">215</span>
    </a>
    <a class="btn btn-default vote-action-bad">
        <span class="icon thumb-down grey black-hover">&nbsp;</span>
        <span class="rating-inbtn">82</span>
    </a>
</span>

我正在使用这个正则表达式来提取评级

a = re.findall('rating-inbtn">(.*?)</span>', webpage)
        like_count = a[0]
        dislike_count = a[1]

但有时 span 类有多个属性“hide-if-zero-113”，在这种情况下我该如何处理这种模式？

谢谢

Answer 1

也许我遗漏了一些东西，但您不需要正则表达式来从代码中提取数字：

data = '''<span class="vote-actions">
    <a class="btn btn-default vote-action-good">
        <span class="icon thumb-up black black-hover">&nbsp;</span>
        <span class="rating-inbtn">215</span>
    </a>
    <a class="btn btn-default vote-action-bad">
        <span class="icon thumb-down grey black-hover">&nbsp;</span>
        <span class="rating-inbtn">82</span>
    </a>
</span>'''

from bs4 import BeautifulSoup

soup = BeautifulSoup(data, 'lxml')

print([span.text for span in soup.select('span.rating-inbtn')])

打印：

['215', '82']

Answer 2

我将扩展给出的其他答案之一。在您的较低示例中，您正在查看两个共享同一个类的元素，这应该足以匹配两个元素。您最上面的示例显示了一个复合类（元素的多个类名），但它再次共享同一类 rating-inbtn。

soup.select('.rating-inbtn')

“.”在哪里是一个 CSS 类选择器。

扩展其他答案：

以后您可以传递以“，”分隔的列表来匹配多个类（实际上是多个选择器），例如

soup.select('.rating-inbtn, .otherClass') 

Answer 3

这取决于您希望添加到表达式的边界。例如，我们可以从：

\s*([a-z0-9-]+)(?:\s+)?([a-z0-9-]+)?\s*

表达式在this demo 的右上角进行了解释，如果您想进一步探索或修改它，在this link 中，您可以逐步观察它如何与一些示例输入进行匹配，如果您喜欢。

---

编辑：

为了捕捉这些评级，这个表达式可能就足够了：

rating-inbtn[^>]+>\s*([^\s<]+)\s*<\/

Demo

用re.findall测试

import re

regex = r"rating-inbtn[^>]+>\s*([^\s<]+)\s*<\/"

test_str = ("<span class=\"vote-actions\">\n"
    "    <a class=\"btn btn-default vote-action-good\">\n"
    "        <span class=\"icon thumb-up black black-hover\">&nbsp;</span>\n"
    "        <span class=\"rating-inbtn\">215</span>\n"
    "    </a>\n"
    "    <a class=\"btn btn-default vote-action-bad\">\n"
    "        <span class=\"icon thumb-down grey black-hover\">&nbsp;</span>\n"
    "        <span class=\"rating-inbtn\">82</span>\n"
    "<span class=\"rating-inbtn\"> 74 </span>\n"
    "<span class=\"rating-inbtn hide-if-zero-113\"> 99 </span>\n"
    "    </a>\n"
    "</span>")

print(re.findall(regex, test_str))

输出

['215', '82', '74', '99']

用re.finditer测试

import re

regex = r"rating-inbtn[^>]+>\s*([^\s<]+)\s*<\/"

test_str = ("<span class=\"vote-actions\">\n"
    "    <a class=\"btn btn-default vote-action-good\">\n"
    "        <span class=\"icon thumb-up black black-hover\">&nbsp;</span>\n"
    "        <span class=\"rating-inbtn\">215</span>\n"
    "    </a>\n"
    "    <a class=\"btn btn-default vote-action-bad\">\n"
    "        <span class=\"icon thumb-down grey black-hover\">&nbsp;</span>\n"
    "        <span class=\"rating-inbtn\">82</span>\n"
    "<span class=\"rating-inbtn\"> 74 </span>\n"
    "<span class=\"rating-inbtn hide-if-zero-113\"> 99 </span>\n"
    "    </a>\n"
    "</span>")

matches = re.finditer(regex, test_str, re.MULTILINE)

for matchNum, match in enumerate(matches, start=1):

    print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group()))

    for groupNum in range(0, len(match.groups())):
        groupNum = groupNum + 1

        print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum)))