from selenium import webdriver
import time

driver = webdriver.Firefox(executable_path=u'C:\Program Files (x86)\Mozilla Firefox\geckodriver.exe')
driver.get('http://www.baidu.com')
time.sleep(0.5)

input = driver.find_element_by_name('wd')
input.clear()
input.send_keys('1234567890')

time.sleep(0.5)
driver.find_element_by_css_selector('#su').click()

D:\Python\Python35-32\python.exe D:/PycharmProjects/untitled1/bai.py
Traceback (most recent call last):
  File "D:/PycharmProjects/untitled1/bai.py", line 10, in <module>
    input.send_keys('1234567890')
  File "D:\Python\Python35-32\lib\site-packages\selenium\webdriver\remote\webelement.py", line 350, in send_keys
    'value': keys_to_typing(value)})
  File "D:\Python\Python35-32\lib\site-packages\selenium\webdriver\remote\webelement.py", line 499, in _execute
    return self._parent.execute(command, params)
  File "D:\Python\Python35-32\lib\site-packages\selenium\webdriver\remote\webdriver.py", line 297, in execute
    self.error_handler.check_response(response)
  File "D:\Python\Python35-32\lib\site-packages\selenium\webdriver\remote\errorhandler.py", line 194, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.WebDriverException: Message: Expected [object Undefined] undefined to be a string