下面的代码实现了模拟提交提交搜索的功能，首先等页面加载完成，然后输入到搜索框文本，点击提交。

from selenium import webdriver
from selenium.webdriver.common.keys import Keys

driver = webdriver.Chrome()
driver.get("http://www.python.org")
assert "Python" in driver.title
elem = driver.find_element_by_name("q")
elem.send_keys("pycon")
elem.send_keys(Keys.RETURN)
print driver.page_source

同样是在 Chrome 里面测试，感受一下。

The driver.get method will navigate to a page given by the URL. WebDriver will wait until the page has fully loaded (that is, the “onload” event has fired) before returning control to your test or script. It’s worth noting that if your page uses a lot of AJAX on load then WebDriver may not know when it has completely loaded.

其中 driver.get 方法会打开请求的URL，WebDriver 会等待页面完全加载完成之后才会返回，即程序会等待页面的所有内容加载完成，JS渲染完毕之后才继续往下执行。注意：如果这里用到了特别多的 Ajax 的话，程序可能不知道是否已经完全加载完毕。

WebDriver offers a number of ways to find elements using one of the find element_by * methods. For example, the input text element can be located by its name attribute using find_element_by_name method

WebDriver 提供了许多寻找网页元素的方法，譬如 find element_by * 的方法。例如一个输入框可以通过 find_element_by_name 方法寻找 name 属性来确定。

Next we are sending keys, this is similar to entering keys using your keyboard. Special keys can be send using Keys class imported from selenium.webdriver.common.keys

然后我们输入来文本然后模拟点击了回车，就像我们敲击键盘一样。我们可以利用 Keys 这个类来模拟键盘输入。 最后最重要的一点 获取网页渲染后的源代码。 输出 page_source 属性即可。 这样，我们就可以做到网页的动态爬取了。

有了以上特性，我们当然可以用来写测试样例了。

import unittest
from selenium import webdriver
from selenium.webdriver.common.keys import Keys

class PythonOrgSearch(unittest.TestCase):

    def setUp(self):
        self.driver = webdriver.Chrome()

    def test_search_in_python_org(self):
        driver = self.driver
        driver.get("http://www.python.org")
        self.assertIn("Python", driver.title)
        elem = driver.find_element_by_name("q")
        elem.send_keys("pycon")
        elem.send_keys(Keys.RETURN)
        assert "No results found." not in driver.page_source

    def tearDown(self):
        self.driver.close()

if __name__ == "__main__":
    unittest.main()

运行程序，同样的功能，我们将其封装为测试标准类的形式。

The test case class is inherited from unittest.TestCase. Inheriting from TestCase class is the way to tell unittest module that this is a test case. The setUp is part of initialization, this method will get called before every test function which you are going to write in this test case class. The test case method should always start with characters test. The tearDown method will get called after every test method. This is a place to do all cleanup actions. You can also call quit method instead of close. The quit will exit the entire browser, whereas close will close a tab, but if it is the only tab opened, by default most browser will exit entirely.

测试用例是继承了 unittest.TestCase 类，继承这个类表明这是一个测试类。setUp方法是初始化的方法，这个方法会在每个测试类中自动调用。每一个测试方法命名都有规范，必须以 test 开头，会自动执行。最后的 tearDown 方法会在每一个测试方法结束之后调用。这相当于最后的析构方法。在这个方法里写的是 close 方法，你还可以写 quit 方法。不过 close 方法相当于关闭了这个 TAB 选项卡，然而 quit 是退出了整个浏览器。当你只开启了一个 TAB 选项卡的时候，关闭的时候也会将整个浏览器关闭。

仅仅抓取页面没有多大卵用，我们真正要做的是做到和页面交互，比如点击，输入等等。那么前提就是要找到页面中的元素。WebDriver提供了各种方法来寻找元素。例如下面有一个表单输入框。

更详细的元素选择方法参见官方文档 元素选择

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

driver = webdriver.Chrome()
driver.get("http://somedomain/url_that_delays_loading")
try:
    element = WebDriverWait(driver, 10).until(
        EC.presence_of_element_located((By.ID, "myDynamicElement"))
    )
finally:
    driver.quit()