概述:
python通过selenium爬取数据是很多突破封锁的有效途径。但在使用selenium中会遇到很多问题,本文就通过一问一答的形式来通熟易懂的普及如何通过selenium执行javascript程序,进而获取动态执行后的网页。如果你喜欢,欢迎转发本文。
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python爬虫编程:用selenium执行javascript出错了,该咋改?
问题:
小明开始学习python爬虫编程了,仿佛整个互联网的数据都快被他纳入囊中了。今天,他又试图完成一个高难度动作,他想让selenium中抓取到以下HTML后,并自动执行js脚本,模仿鼠标自动执行一个点击动作。但令他很失望的是,居然,居然,没用!
<div class="vbseo_liked">
<a href="http://www.jamiiforums.com/member.php?u=8355" rel="nofollow">Nyaralego</a>
,
<a href="http://www.jamiiforums.com/member.php?u=8870" rel="nofollow">Sikonge</a>
,
<a href="http://www.jamiiforums.com/member.php?u=8979" rel="nofollow">Ab-Titchaz</a>
and
<a onclick="return vbseoui.others_click(this)" href="http://www.jamiiforums.com/kenyan-news/225589-kenyan-and-tanzanian-surburbs.html#">11 others</a>
like this.
</div>
这是他执行的代码。
browser.execute_script("document.getElement(By.xpath(\"//div[@class='vbseo_liked']/a[contains(@onclick, 'return vbseoui.others_click(this)')]\").click()")
它没用,没有反应。究竟做错了什么?
Python大大的答案:
要点回答:
使用selenium查找元素并将其传递execute_script()给单击:
link = browser.find_element_by_xpath('//div[@class="vbseo_liked"]/a[contains(@onclick, "return vbseoui.others_click(this)")]')
browser.execute_script('arguments[0].click();', link)
如果要从头解决这问题,那么以下就是需要了解它的一系列事情:
如何使用JavaScript模拟点击?
这就是我做的东西。这很简单,但它有效:
function eventFire(el, etype){
if (el.fireEvent) {
el.fireEvent('on' + etype);
} else {
var evObj = document.createEvent('Events');
evObj.initEvent(etype, true, false);
el.dispatchEvent(evObj);
}
}
用法:
eventFire(document.getElementById('mytest1'), 'click');
如何在Python里进行模拟点击呢?首先制定一个自定义的预期条件,等待元素被“执行”:
class wait_for_text_not_to_end_with(object):
def __init__(self, locator, text):
self.locator = locator
self.text = text
def __call__(self, driver):
try :
element_text = EC._find_element(driver, self.locator).text.strip()
return not element_text.endswith(self.text)
except StaleElementReferenceException:
return False
定义完毕后,如何在程序里调用这个类呢?看看以下代码:
from selenium import webdriver
from selenium.common.exceptions import StaleElementReferenceException
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
class wait_for_text_not_to_end_with(object):
def __init__(self, locator, text):
self.locator = locator
self.text = text
def __call__(self, driver):
try :
element_text = EC._find_element(driver, self.locator).text.strip()
return not element_text.endswith(self.text)
except StaleElementReferenceException:
return False
browser = webdriver.PhantomJS()
browser.maximize_window()
browser.get("http://www.jamiiforums.com/kenyan-news/225589-kenyan-and-tanzanian-surburbs.html")
username = browser.find_element_by_id("navbar_username")
password = browser.find_element_by_name("vb_login_password_hint")
username.send_keys("MarioP")
password.send_keys("codeswitching")
browser.find_element_by_class_name("loginbutton").click()
wait = WebDriverWait(browser, 30)
wait.until(EC.visibility_of_element_located((By.XPATH, '//h2[contains(., "Redirecting")]')))
wait.until(EC.title_contains('Kenyan & Tanzanian'))
wait.until(EC.visibility_of_element_located((By.ID, 'postlist')))
# click "11 others" link
link = browser.find_element_by_xpath('//div[@class="vbseo_liked"]/a[contains(@onclick, "return vbseoui.others_click(this)")]')
link.click()
browser.execute_script("""
function eventFire(el, etype){
if (el.fireEvent) {
el.fireEvent('on' + etype);
} else {
var evObj = document.createEvent('Events');
evObj.initEvent(etype, true, false);
el.dispatchEvent(evObj);
}
}
eventFire(arguments[0], "click");
""", link)
# wait for the "div" not to end with "11 others link this."
wait.until(wait_for_text_not_to_end_with((By.CLASS_NAME, 'vbseo_liked'), "11 others like this."))
print 'success!!'
browser.close()
看,如何在python里通过selenium来爬取数据就是这么简单。要点掌握好,开始编制自己的爬虫吧。
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