Question

例如，我有网页http://www.amazon.com/dp/1597805483。

我想用xpath来抓取这句话Of all the sports played across the globe, none has more curses and superstitions than baseball, America’s national pastime.

page = requests.get(url)
tree = html.fromstring(page.text)
feature_bullets = tree.xpath('//*[@id="iframeContent"]/div/text()')
print feature_bullets

上述代码没有返回任何内容。原因是浏览器解释的xpath与源代码不同。但我不知道如何从源代码中获取xpath。

Answer 1

构建您正在抓取网页的页面涉及很多内容。

至于描述，具体来说，底层HTML是在javascript函数中构建的：

<script type="text/javascript">

    P.when('DynamicIframe').execute(function (DynamicIframe) {
        var BookDescriptionIframe = null,
                bookDescEncodedData = "%3Cdiv%3E%3CB%3EA%20Fantastic%20Anthology%20Combining%20the%20Love%20of%20Science%20Fiction%20with%20Our%20National%20Pastime%3C%2FB%3E%3CBR%3E%3CBR%3EOf%20all%20the%20sports%20played%20across%20the%20globe%2C%20none%20has%20more%20curses%20and%20superstitions%20than%20baseball%2C%20America%26%238217%3Bs%20national%20pastime.%3Cbr%3E%3CBR%3E%3CI%3EField%20of%20Fantasies%3C%2FI%3E%20delves%20right%20into%20that%20superstition%20with%20short%20stories%20written%20by%20several%20key%20authors%20about%20baseball%20and%20the%20supernatural.%20%20Here%20you%27ll%20encounter%20ghostly%20apparitions%20in%20the%20stands%2C%20a%20strangely%20charming%20vampire%20double-play%20combination%2C%20one%20fan%20who%20can%20call%20every%20shot%20and%20another%20who%20can%20see%20the%20past%2C%20a%20sad%20alternate-reality%20for%20the%20game%27s%20most%20famous%20player%2C%20unlikely%20appearances%20on%20the%20field%20by%20famous%20personalities%20from%20Stephen%20Crane%20to%20Fidel%20Castro%2C%20a%20hilariously%20humble%20teenage%20phenom%2C%20and%20much%20more.%20In%20this%20wonderful%20anthology%20are%20stories%20from%20such%20award-winning%20writers%20as%3A%3CBR%3E%3CBR%3EStephen%20King%20and%20Stewart%20O%26%238217%3BNan%3Cbr%3EJack%20Kerouac%3CBR%3EKaren%20Joy%20Fowler%3CBR%3ERod%20Serling%3CBR%3EW.%20P.%20Kinsella%3CBR%3EAnd%20many%20more%21%3CBR%3E%3CBR%3ENever%20has%20a%20book%20combined%20the%20incredible%20with%20great%20baseball%20fiction%20like%20%3CI%3EField%20of%20Fantasies%3C%2FI%3E.%20This%20wide-ranging%20collection%20reaches%20from%20some%20of%20the%20earliest%20classics%20from%20the%20pulp%20era%20and%20baseball%27s%20golden%20age%2C%20all%20the%20way%20to%20material%20appearing%20here%20for%20the%20first%20time%20in%20a%20print%20edition.%20Whether%20you%20love%20the%20game%20or%20just%20great%20fiction%2C%20these%20stories%20will%20appeal%20to%20all%2C%20as%20the%20writers%20in%20this%20anthology%20bring%20great%20storytelling%20of%20the%20strange%20and%20supernatural%20to%20the%20plate%2C%20inning%20after%20inning.%3CBR%3E%3C%2Fdiv%3E",
                bookDescriptionAvailableHeight,
                minBookDescriptionInitialHeight = 112,
                options = {};
    ...

</script>

这里的想法是获取脚本标记的文本，使用正则表达式提取描述值，取消引用HTML，用lxml.html解析并获取.text_content()：

import re
from urlparse import unquote

from lxml import html
import requests

url = "http://rads.stackoverflow.com/amzn/click/1597805483"
page = requests.get(url, headers={'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36'})
tree = html.fromstring(page.content)

script = tree.xpath('//script[contains(., "bookDescEncodedData")]')[0]
match = re.search(r'bookDescEncodedData = "(.*?)",', script.text)
if match:
    description_html = html.fromstring(unquote(match.group(1)))
    print description_html.text_content()

打印：

A Fantastic Anthology Combining the Love of Science Fiction with Our National Pastime. 
Of all the sports played across the globe, none has more curses and superstitions than baseball, America’s national pastime.Field of Fantasies delves right into that superstition with short stories written by several key authors about baseball and the supernatural.  
Here you'll encounter ghostly apparitions in the stands, a strangely charming vampire double-play combination, one fan who can call every shot and another who can see the past, a sad alternate-reality for the game's most famous player, unlikely appearances on the field by famous personalities from Stephen Crane to Fidel Castro, a hilariously humble teenage phenom, and much more. 
In this wonderful anthology are stories from such award-winning writers as:Stephen King and Stewart O’NanJack KerouacKaren Joy FowlerRod SerlingW. P. KinsellaAnd many more!Never has a book combined the incredible with great baseball fiction like Field of Fantasies. 
This wide-ranging collection reaches from some of the earliest classics from the pulp era and baseball's golden age, all the way to material appearing here for the first time in a print edition. Whether you love the game or just great fiction, these stories will appeal to all, as the writers in this anthology bring great storytelling of the strange and supernatural to the plate, inning after inning.

类似的解决方案，但使用BeautifulSoup：

import re
from urlparse import unquote

from bs4 import BeautifulSoup
import requests

url = "http://rads.stackoverflow.com/amzn/click/1597805483"
page = requests.get(url, headers={'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36'})
soup = BeautifulSoup(page.content)

script = soup.find('script', text=lambda x:'bookDescEncodedData' in x)
match = re.search(r'bookDescEncodedData = "(.*?)",', script.text)
if match:
    description_html = BeautifulSoup(unquote(match.group(1)))
    print description_html.text

或者，您可以采用高级方法并在selenium的帮助下使用真正的浏览器：

from selenium import webdriver

url = "http://rads.stackoverflow.com/amzn/click/1597805483"

driver = webdriver.Firefox()
driver.get(url)

iframe = driver.find_element_by_id('bookDesc_iframe')
driver.switch_to.frame(iframe)

print driver.find_element_by_id('iframeContent').text

driver.close()

生成更好的格式化输出：

A Fantastic Anthology Combining the Love of Science Fiction with Our National Pastime

Of all the sports played across the globe, none has more curses and superstitions than baseball, America’s national pastime.

Field of Fantasies delves right into that superstition with short stories written by several key authors about baseball and the supernatural. Here you'll encounter ghostly apparitions in the stands, a strangely charming vampire double-play combination, one fan who can call every shot and another who can see the past, a sad alternate-reality for the game's most famous player, unlikely appearances on the field by famous personalities from Stephen Crane to Fidel Castro, a hilariously humble teenage phenom, and much more. In this wonderful anthology are stories from such award-winning writers as:

Stephen King and Stewart O’Nan
Jack Kerouac
Karen Joy Fowler
Rod Serling
W. P. Kinsella
And many more!

Never has a book combined the incredible with great baseball fiction like Field of Fantasies. This wide-ranging collection reaches from some of the earliest classics from the pulp era and baseball's golden age, all the way to material appearing here for the first time in a print edition. Whether you love the game or just great fiction, these stories will appeal to all, as the writers in this anthology bring great storytelling of the strange and supernatural to the plate, inning after inning.

如何在python中的网页上抓取嵌入式脚本

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