python+selenium下载不了pdf文件

正常下载pdf python代码如下

import os

from selenium import webdriver
from time import sleep

fp = webdriver.FirefoxProfile()

fp.set_preference("browser.download.folderList",2)
fp.set_preference("browser.download.manager.showWhenStarting",False)
fp.set_preference("browser.download.dir", "c:\\test")
fp.set_preference("browser.helperApps.neverAsk.saveToDisk", "application/pdf")

browser = webdriver.Firefox(firefox_profile=fp)

browser.get('http://sahitest.com/demo/saveAs.htm')
driver.find_element_by_xpath('/html/body/a[2]').click()
sleep(3)
browser.quit()

但我告诉你 这样是下载不下来的  

正确的下载方式是这样的  一定要加上我标红的这二句  吐血的经验

# -*- coding: utf-8 -*-

from selenium import webdriver
from time import sleep

fp = webdriver.FirefoxProfile()
fp.set_preference("browser.download.folderList", 2)
fp.set_preference("browser.download.manager.showWhenStarting", False)
fp.set_preference("browser.download.dir", "c:\\test")
fp.set_preference("plugin.disable_full_page_plugin_for_types", "application/pdf")
fp.set_preference("pdfjs.disabled", True)
fp.set_preference("browser.helperApps.neverAsk.saveToDisk", "application/pdf")

driver = webdriver.Firefox(firefox_profile=fp)
driver.implicitly_wait(10)
driver.maximize_window()
driver.get('http://sahitest.com/demo/saveAs.htm')
driver.find_element_by_xpath('/html/body/a[2]').click()
sleep(3)
#driver.quit()