如上图，js 语句在控制台可以取到 value 值，但在 python 脚本中 print 出来却为 NONE

class mailGroupChatTest(unittest.TestCase):

    def setUp(self):
        desired_caps = {}
        desired_caps['platformName'] = GlobalVar.platformName
        desired_caps['platformVersion'] = GlobalVar.platformVersion_7
        desired_caps['deviceName'] = GlobalVar.deviceName
        desired_caps['appPackage'] = GlobalVar.appPackage_7
        desired_caps['appActivity'] = GlobalVar.appActivity_7
        desired_caps['fullReset'] = 'false'
        desired_caps['unicodeKeyboard'] = 'True'
        desired_caps['resetKeyboard'] = 'True'
        desired_caps['fastReset'] = 'false'
        self.dr = webdriver.Remote('http://localhost:4723/wd/hub', desired_caps)

    def tearDown(self):
        self.dr.quit()

    def test_mailGroupChat(self):

        actionEvent.login.go_loginPage(self)  # 访问登录页
        actionEvent.login.login(self, GlobalVar.wudi_email, GlobalVar.wudi_name)  # wudi登录OA
        js = 'document.getElementById("272dffca-edf3-4bcf-98f8-996180dff194").value'
        ele = self.dr.execute_script(js)
        print(ele)

if __name__ == '__main__':
    suite = unittest.TestLoader().loadTestsFromTestCase(mailGroupChatTest)
    unittest.TextTestRunner(verbosity=2).run(suite)

执行结果：
D:\AutoWork\Python\python.exe "D:\AutoWork\Pycharm\PyCharm Community Edition 2017.1.2\helpers\pycharm_jb_unittest_runner.py" --path D:/AutoWork/自动化测试项目/Milan_H5_Auto/test_case/debug_test.py
Testing started at 10:07 ...
Launching unittests with arguments python -m unittest D:/AutoWork/自动化测试项目/Milan_H5_Auto/test_case/debug_test.py in D:\AutoWork\自动化测试项目\Milan_H5_Auto\test_case

None

Ran 1 test in 45.708s

OK

Process finished with exit code 0

问题：
python 调用 js 语句如何才能获取 input 属性元素的值