python正则表达式查找并替换具有特定属性值的html标签答案

【问题标题】：python regular expression find and replace html tag with specific attribute valuepython正则表达式查找并替换具有特定属性值的html标签
【发布时间】：2013-12-17 16:57:56
【问题描述】：

我正在尝试在 python 中编写一个正则表达式，它将找到所有 src 属性等于特定值的 img 标签。我尝试编写以下内容

   # where thm equal /public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82
   p = re.compile(r'<img.*?%s.*?>' % thm)
   print p.pattern
   print p.sub(linked_image, c)

低于我得到的输出

<img.*?/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82.*?>

<p><img src="/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82" alt=""></p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf </p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf 
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf

【问题讨论】：

在这项工作中使用 BeautifulSoup 怎么样？ crummy.com/software/BeautifulSoup
我可以使用 beautifulSoup，但正在更改非结构化内容，它应该保持其结构不变。 BeautifulSoup 的问题，我将无法将处理后的汤输出到以前的结构作为输出...这就是为什么我需要更改替换字符串方法
请看一下新版本——我在原始的thm变量中发现了错误，并在下面提出了两个解决方案。

标签： python regex

【解决方案1】：

使用 LXML 的解决方案

为了将解决方案与正则表达式和 LXML 进行比较，我创建了另一个帖子：

更简单、更稳定的解决方案是将lxml 与etree 结合使用。在那个解决方案中，你访问某些 DOM 元素并编辑它们。

转换 HTML 字符串并通过正确的xpath 获取它，例如.//img。 xpath 返回所有找到的元素列表，您可以在其中找到 get 和 set src 属性。函数etree.tostring(tree) 返回一个编辑后的字符串：

from lxml import etree
tree = etree.HTML('''<html>
                     <body>
                        <h1>Title</h1>
                        <img src="/media/old/another_logo.png" alt="" />
                        <p>Lorem Ipsum</p>
                        <p><img src="/media/old/logo.png" alt=""/></p>
                     </body>
                  </html>''')

imgs = tree.xpath('.//img')

for img in imgs:
    print 'OLD_SOURCE', img.get('src')
    img.set('src', '/media/new/python.jpg')

print etree.tostring(tree)

输出

OLD_SOURCE /media/old/another_logo.png
OLD_SOURCE /media/old/logo.png

<html>
    <body>
        <h1>Title</h1>
            <img src="/media/new/python.jpg" alt=""/>
            <p>Lorem Ipsum</p>
            <p><img src="/media/new/python.jpg" alt=""/></p>
    </body>
</html>

【讨论】：

【解决方案2】：

正则表达式解决方案：

我意识到插入thm 的字符串没有被转义。因此，在将其添加到正则表达式之前，您需要使用转义所有符号正则表达式语言中的附加含义 - 这里是? 和.。

我将? 替换为[?]{1}，将. 替换为\.。生成的正则表达式现在匹配测试字符串。

import re
thm = '/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82'

all_html_code = '''<img.*?/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82.*?>

<p><img src="/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82" alt=""></p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf </p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf
</p><p>lksj lksdfj lsdkfj sldkfj sldkfj lskdfj lsjf lksjf lksj flksdjf klsj flk dkj sdlkfj sdlkfj sldkjf sldkfj lsdkjf lskjflsjfsl lksdjf '''

escaped_thm = thm.replace('.', '\.').replace('?','[?]{1}')
p = re.compile(r'<img.*?src="(%s)".*?>' % escaped_thm)

test_img = '''<img src="/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82" alt="">'''
print p.match(test_img)

new_img_tag = '<img src="/python/logo.jpg" alt=""/>'
print p.sub(new_img_tag, all_html_code)

对了，你为什么要找<img src=""...>？您可以直接替换 src 属性：

escaped_thm = thm.replace('.', '\.').replace('?','[?]{1}')
p = re.compile(r'src="(%s)"' % escaped_thm)

replacement = '''src="/python/logo.jpg"'''
print p.sub(replacement, all_html_code)

输出 1

<_sre.SRE_Match object at 0x... >
<img.*?/public_media/cache/84/b5/84b59e293cbdb7041b68a84977d62cf3.jpg?image_pk=82.*?>

<p><img src="/python/logo.jpg" alt=""/></p><p>lksj lksdfj ... lksdjf

输出 2

<p><img src="/python/logo.jpg" alt=""></p><p>lksj lksdfj ... lksdjf

在询问了转义正则表达式符号的正确方法 (Regular expression to escape regular expressions) 之后 - 我可以推荐一个 re.escape 而不是两个 replace 方法。

使用 LXML

你需要使用正则表达式吗？ HTML 的正则表达式可能存在很大问题。在此处查看更多信息和精彩帖子（RegEx match open tags except XHTML self-contained tags）。

我宁愿像这里那样使用 XPath。

【讨论】：

我可以使用 beautifulSoup，但正在更改非结构化内容，它应该保持其结构不变。 BeautifulSoup 的问题，我将无法将处理后的汤输出到以前的结构作为输出...这就是为什么我需要更改替换字符串方法
我用正则表达式添加了一个解决方案。请查看上面的示例。