菜鸟求助！！ webdriver基于python，封装登录脚本时报错 - 51Testing软件测试论坛

from public import browser
from public import login
from selenium import webdriver

browser().firefox("此处是url")
yonghu = login("此处是username","此处是password")
yonghu.denglu()

#####public.py#####

from selenium import webdriver
import os
class browser():
# webdriver for chrome
def chrome(self,url,driverpath):
      os.environ["webdriver.chrome.driver"] = driverpath
      driver = webdriver.Chrome()
      driver.get(url)

# webdriver for firefox
def firefox(self,url):
      driver = webdriver.Firefox()
      driver.get(url)

#login
class login():
def __init__(self,username,password):
      self.name = username
      self.password = password

def denglu(self):
      driver = webdriver()
      driver.find_element_by_xpath("//*[@id='TANGRAM__PSP_4__userName']").send_keys(self.name)
      driver.find_element_by_id("TANGRAM__PSP_4__password").send_keys(self.password)
      driver.find_element_by_xpath("//*[@id='TANGRAM__PSP_4__submit']").click()
      text = driver.find_element_by_id("TANGRAM__PSP_4__error").text

报错内容！！
Traceback (most recent call last):
  File "F:\Workplace\Python auto testing\src\new1\__init__.py", line 6, in <module>
yonghu = login("此处是username","此处是password")
  File "F:\Workplace\Python auto testing\src\new1\public.py", line 19, in __init__
a = self.driver
AttributeError: login instance has no attribute 'driver'