BeautifulSoup find_all（）找不到所有请求的元素

Question

我在BeautifulSoup中看到了一些奇怪的行为，如以下示例所示。

import re
from bs4 import BeautifulSoup
html = """<p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>
<p class='blue'>This paragraph has a color of blue.</p>
<p>This paragraph does not have a color.</p>"""
soup = BeautifulSoup(html, 'html.parser')
pattern = re.compile('color', flags=re.UNICODE+re.IGNORECASE)
paras = soup.find_all('p', string=pattern)
print(len(paras)) # expected to find 3 paragraphs with word "color" in it
  2
print(paras[0].prettify())
  <p class="blue">
    This paragraph as a color of blue.
  </p>

print(paras[1].prettify())
  <p>
    This paragraph does not have a color.
  </p>

如您所见，由于某些原因， <p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>第一段<p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p> <p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>不会被find_all(...)拾取， find_all(...)我不知道为什么不这样做。

Answer 1

string属性希望标签仅包含文本，而不包含标签。 如果您尝试为第一个p标签打印.string ，它将返回None ，因为它包含标签。

或者，为了更好地解释它， 文档中说：

如果标签只有一个子代，并且该子代是NavigableString ，则该子代可以作为.string

如果标签包含多个内容，则不清楚.string应该指向什么，因此.string被定义为None

解决此问题的方法是使用lambda函数。

html = """<p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>
<p class='blue'>This paragraph has a color of blue.</p>
<p>This paragraph does not have a color.</p>"""
soup = BeautifulSoup(html, 'html.parser')

first_p = soup.find('p')
print(first_p)
# <p style="color: red;">This has a <b>color</b> of red. Because it likes the color red</p>
print(first_p.string)
# None
print(first_p.text)
# This has a color of red. Because it likes the color red

paras = soup.find_all(lambda tag: tag.name == 'p' and 'color' in tag.text.lower())
print(paras)
# [<p style="color: red;">This has a <b>color</b> of red. Because it likes the color red</p>, <p class="blue">This paragraph has a color of blue.</p>, <p>This paragraph does not have a color.</p>]

Answer 2

如果要掌握'p' ，则可以执行以下操作：

import re
from bs4 import BeautifulSoup
html = """<p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>
<p class='blue'>This paragraph has a color of blue.</p>
<p>This paragraph does not have a color.</p>"""
soup = BeautifulSoup(html, 'html.parser')

paras = soup.find_all('p')
for p in paras:
  print (p.get_text())

Answer 3

我实际上还没有弄清楚为什么指定find_all(...)的字符串（或文本，对于BeautifulSoup的较早版本为文本）参数没有给我想要的东西，但是以下内容find_all(...)了我一个通用的解决方案。

pattern = re.compile('color', flags=re.UNICODE+re.IGNORECASE)
desired_tags = [tag for tag in soup.find_all('p') if pattern.search(tag.text) is not None]