python webdriver 报错WebDriverException: Message: can't access dead object的原因（pycharm中）

PyCharm中运行firefox webdriver访问邮箱添加通讯录的时候报错-WebDriverException: Message: can't access dead object

调了半天，发现是因为在登录操作后没有从frame中切换出来导致的，因为在登录的时候需要先切换到frame中，登录之后要切换出来才能继续其他操作。

下面是我运行的代码，driver.switch_to.default_content()这一行被我注释掉了，结果就报这个错

代码：
driver=webdriver.Firefox(executable_path='c:\geckodriver')
driver.get('http://mail.126.com')
try:
    wait=WebDriverWait(driver,10,0.2)#显示等待
    driver.switch_to.frame(driver.find_element_by_xpath("//iframe[@id='x-URS-iframe']"))#切换到用户名和密码输入框所在的frame元素

    name=wait.until(lambda x:x.find_element_by_xpath("//input[@placeholder='邮箱帐号或手机号' and @name='email']"))
    name.send_keys('xiaxiaoxu1987')
    password=wait.until(lambda x:x.find_element_by_xpath("//input[@placeholder='密码']"))
    password.send_keys('gloryroad')
    submit=wait.until(lambda x:x.find_element_by_xpath("//a[@id='dologin']"))
    submit.click()
    #driver.switch_to.default_content()#在pycharm里用switch_to_default_content()会被加删除线，out了

    address_book_link=wait.until(lambda x:x.find_element_by_xpath("//div[text()='通讯录']"))
    address_book_link.click()

运行报错：

C:Python27python.exe D:/test/dataDrivenTestPractice1/PageObject/test.py
Traceback (most recent call last):
  File "D:/test/dataDrivenTestPractice1/PageObject/test.py", line 27, in <module>
    address_book_link=wait.until(lambda x:x.find_element_by_xpath("//div[text()='通讯录']"))
  File "C:Python27libsite-packagesseleniumwebdriversupportwait.py", line 71, in until
    value = method(self._driver)
  File "D:/test/dataDrivenTestPractice1/PageObject/test.py", line 27, in <lambda>
    address_book_link=wait.until(lambda x:x.find_element_by_xpath("//div[text()='通讯录']"))
  File "C:Python27libsite-packagesseleniumwebdriver emotewebdriver.py", line 387, in find_element_by_xpath
    return self.find_element(by=By.XPATH, value=xpath)
  File "C:Python27libsite-packagesseleniumwebdriver emotewebdriver.py", line 957, in find_element
    'value': value})['value']
  File "C:Python27libsite-packagesseleniumwebdriver emotewebdriver.py", line 314, in execute
None
    self.error_handler.check_response(response)
  File "C:Python27libsite-packagesseleniumwebdriver emoteerrorhandler.py", line 242, in check_response
    raise exception_class(message, screen, stacktrace)
WebDriverException: Message: can't access dead object


Process finished with exit code 0

把注释去掉：

driver=webdriver.Firefox(executable_path='c:\geckodriver')
driver.get('http://mail.126.com')
try:
    wait=WebDriverWait(driver,10,0.2)#显示等待
    driver.switch_to.frame(driver.find_element_by_xpath("//iframe[@id='x-URS-iframe']"))#切换到用户名和密码输入框所在的frame元素

    name=wait.until(lambda x:x.find_element_by_xpath("//input[@placeholder='邮箱帐号或手机号' and @name='email']"))
    name.send_keys('xiaxiaoxu1987')
    password=wait.until(lambda x:x.find_element_by_xpath("//input[@placeholder='密码']"))
    password.send_keys('gloryroad')
    submit=wait.until(lambda x:x.find_element_by_xpath("//a[@id='dologin']"))
    submit.click()
    driver.switch_to.default_content()#在pycharm里用switch_to_default_content()会被加删除线，out了

    address_book_link=wait.until(lambda x:x.find_element_by_xpath("//div[text()='通讯录']"))
    address_book_link.click()

结果：没有报错

C:Python27python.exe D:/test/dataDrivenTestPractice1/PageObject/test.py

Process finished with exit code 0