python - BeautifulSoup find_all() 未找到所有请求的元素

Question

我在 BeautifulSoup 中发现了一些奇怪的行为，如下面的示例所示。

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>

正如您所看到的，由于某种原因<p style='color: red;'>This has a <b>color</b> of red. Because it likes the color red</p>的第一段没有被 find_all(...) 拾取我不明白为什么不。

Answer 1

string 属性期望标记仅包含文本而不包含标记。如果您尝试为第一个 p 标记打印 .string，它将返回 None，因为它包含标记。

或者，为了更好地解释它，documentation说:

If a tag has only one child, and that child is a NavigableString, the child is made available as .string

If a tag contains more than one thing, then it’s not clear what .string should refer to, so .string is defined to be None

克服这个问题的方法是使用 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>]