本机环境：xamppv3.2.1+ecshop3.0  
1.元素定位写对，却一直报错，发现是页面元素加载的太慢，所以加上延时

from selenium import webdriver
import time
driver=webdriver.Chrome()
driver.implicitly_wait(10)     

 #自动延时10s
driver.get("http://localhost/ecshop")
# driver.find_element_by_xpath('//div[@class="fl cart-yh"]/a').click()
driver.find_element_by_xpath("//a[@href='user.php']").click()

# 登陆
driver.find_element_by_name("username").send_keys("zach")
driver.find_element_by_name('password').send_keys("123456")
driver.find_element_by_name("submit").click()
# 选择商品
time.sleep(3)
driver.find_element_by_xpath("//img[@src='images/201605/thumb_img/72_thumb_G_1462956048008.jpg']").click()
driver.find_element_by_xpath("//img[@src='themes/default/images/buybtn1.png']").click()    #立即购买
# driver.find_element_by_xpath("/html/body/div[6]/div[1]/table/tbody/tr/td[2]/a/img").click()   #结算
driver.find_element_by_xpath("//img[@src='themes/default/images/checkout.gif']").click()

#选择城市  下拉框 1.两次定位  2.xpath 定位层级标签
province = driver.find_element_by_name("province")
province.find_element_by_xpath("//option[@value='5']").click()
city = driver.find_element_by_id("selCities_0")
city.find_element_by_xpath("//option[@value='50']").click()

driver.find_element_by_xpath("//select[@name='district']/option[3]").click()

driver.find_element_by_id("consignee_0").send_keys('张三')
driver.find_element_by_id("address_0").send_keys("深圳市宝安区")
driver.find_element_by_id("tel_0").send_keys("18888888888")
driver.find_element_by_class_name("bnt_blue_2").click()
#付款
time.sleep(3)
driver.find_element_by_xpath("//input[@name='shipping' and @value='5']").click()

driver.find_element_by_xpath("//*[@id='paymentTable']/tbody/tr[4]/td[1]/input").click()
driver.find_element_by_xpath("//input[@src='themes/default/images/bnt_subOrder.gif']").click()