Question

我在Python 2.7中发现，如果我使用bs4.BeautifulSoup.find_all构建器，则无法执行非递归lxml。

采用以下示例HTML代码段：

<p> <b> Cats </b> are interesting creatures </p>

<p> <b> Dogs </b> are cool too </p>

<div>
<p> <b> Penguins </b> are pretty neat, but they're inside a div </p>
</div>

<p> <b> Llamas </b> don't live in New York </p>

说我想找到所有直接孩子的p元素。我使用find_all执行非递归find_all("p", recursive=False)。

为了对此进行测试，我将上述HTML代码段设置为名为html的变量。然后，我创建了两个BeautifulSoup个实例，a和b：

a = bs4.BeautifulSoup(html, "html.parser")
b = bs4.BeautifulSoup(html, "lxml")

正常使用find_all时，它们都能正常运行：

>>> a.find_all("p")
[<p> <b> Cats </b> are interesting creatures </p>, <p> <b> Dogs </b> are cool too </p>, <p> <b> Penguins </b> are pretty neat, but they're inside a div </p>, <p> <b> Llamas </b> don't live in New York </p>]
>>> b.find_all("p")
[<p> <b> Cats </b> are interesting creatures </p>, <p> <b> Dogs </b> are cool too </p>, <p> <b> Penguins </b> are pretty neat, but they're inside a div </p>, <p> <b> Llamas </b> don't live in New York </p>]

但如果我关闭递归查找，则只有a有效。 b返回一个空列表：

>>> a.find_all("p", recursive=False)
[<p> <b> Cats </b> are interesting creatures </p>, <p> <b> Dogs </b> are cool too </p>, <p> <b> Llamas </b> don't live in New York </p>]
>>> b.find_all("p", recursive=False)
[]

这是为什么？这是一个错误，还是我做错了什么？ lxml构建器是否支持非递归find_all？

Answer 1

这是因为lxml解析器会将您的HTML代码放入html/body（如果不存在）：

>>> b = bs4.BeautifulSoup(html, "lxml")
>>> print(b)
<html><body><p> <b> Cats </b> are interesting creatures </p>
<p> <b> Dogs </b> are cool too </p>
<div>
<p> <b> Penguins </b> are pretty neat, but they're inside a div </p>
</div>
<p> <b> Llamas </b> don't live in New York </p>
</body></html>

因此，非递归模式中的find_all()会尝试在html元素中找到元素，该元素只有body子元素：

>>> print(b.find_all("p", recursive=False))
[]
>>> print(b.body.find_all("p", recursive=False))
[<p> <b> Cats </b> are interesting creatures </p>, <p> <b> Dogs </b> are cool too </p>, <p> <b> Llamas </b> don't live in New York </p>]

使用lxml构建器进行非递归查找

1 个答案: