Beautifulsoup：.find() 和 .select() 之间有区别吗 - python 3.xx
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/38028384/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Beautifulsoup : Is there a difference between .find() and .select() - python 3.xx
提问by Dieter
I've a simple question:
我有一个简单的问题：
when you use BeautifulSoupto scrape a certain part of a website, you can use data.find(), data.findAll()or data.select().
当您使用BeautifulSoup抓取网站的某个部分时，您可以使用data.find(),data.findAll()或data.select()。
Now the question is. Is there a significant difference between the .find()and the .select()methods?
(e.g. in performance or flexibility, or ...)
现在的问题是。.find()和.select()方法之间有显着差异吗？（例如在性能或灵活性方面，或...）
or are they just the same?
或者他们只是一样？
Kind regards
亲切的问候
回答by Padraic Cunningham
To summarise the comments:
总结评论：
- selectfinds multiple instances and returns a list, findfinds the first, so they don't do the same thing. select_onewould be the equivalent to find.
- I almost always use css selectors when chaining tags or using tag.classname, if looking for a single element without a class I use find. Essentially it comes down to the use case and personal preference.
- As far as flexibility goes I think you know the answer,
soup.select("div[id=foo] > div > div > div[class=fee] > span > span > a")would look pretty ugly using multiple chained find/find_allcalls. - The only issue with the css selectors in bs4 is the very limited support, nth-of-typeis the only pseudo class implemented and chaining attributes like a[href][src] is also not supported as are many other parts of css selectors. But things like a[href=..]* , a[href^=], a[href$=]etc.. are I think much nicer than
find("a", href=re.compile(....))but again that is personal preference.
- select找到多个实例并返回一个列表，find找到第一个，所以它们不会做同样的事情。select_one相当于find。
- 我几乎总是在链接标签或使用tag.classname时使用 css 选择器，如果我使用find 寻找没有类的单个元素。从本质上讲，它归结为用例和个人偏好。
- 就灵活性而言，我认为您知道答案，
soup.select("div[id=foo] > div > div > div[class=fee] > span > span > a")使用多个链接的find/find_all调用看起来非常难看。 - bs4 中 css 选择器的唯一问题是支持非常有限，nth-of-type是唯一实现的伪类，并且像 css 选择器的许多其他部分一样不支持像 a[href][src] 这样的链接属性。但是像a[href=..]* 、a[href^=]、a[href$=]等。我认为比这要好得多，
find("a", href=re.compile(....))但这又是个人喜好。
For performance we can run some tests, I modified the code from an answer hererunning on 800+ html files taken from here, is is not exhaustive but should give a clue to the readability of some of the options and the performance:
出于性能，我们可以运行一些测试，我修改从代码这里的答案上800+的HTML文件运行取自这里，是不是全部，但应该给一个线索的一些选项和性能可读性：
The modified functions are:
修改后的函数是：
from bs4 import BeautifulSoup
from glob import iglob
def parse_find(soup):
author = soup.find("h4", class_="h12 talk-link__speaker").text
title = soup.find("h4", class_="h9 m5").text
date = soup.find("span", class_="meta__val").text.strip()
soup.find("footer",class_="footer").find_previous("data", {
"class": "talk-transcript__para__time"}).text.split(":")
soup.find_all("span",class_="talk-transcript__fragment")
def parse_select(soup):
author = soup.select_one("h4.h12.talk-link__speaker").text
title = soup.select_one("h4.h9.m5").text
date = soup.select_one("span.meta__val").text.strip()
soup.select_one("footer.footer").find_previous("data", {
"class": "talk-transcript__para__time"}).text
soup.select("span.talk-transcript__fragment")
def test(patt, func):
for html in iglob(patt):
with open(html) as f:
func(BeautifulSoup(f, "lxml")
Now for the timings:
现在是时间：
In [7]: from testing import test, parse_find, parse_select
In [8]: timeit test("./talks/*.html",parse_find)
1 loops, best of 3: 51.9 s per loop
In [9]: timeit test("./talks/*.html",parse_select)
1 loops, best of 3: 32.7 s per loop
Like I said not exhaustive but I think we can safely say the css selectors are definitely more efficient.
就像我说的并不详尽，但我认为我们可以有把握地说 css 选择器肯定更有效。
