一种通过value的值：

def a(self,driver,element,value):

     xpath = '//option[@value="'+value+'"]'

    select = driver.find_element_by_xpath(element) #查找到select控件，这里通过xpath查找

    select.find_element_by_xpath(xpath).click()

一种通过下拉框文本：

def b(self,driver,element,value):

    select = driver.find_element_by_id(element) #查找到select控件，这里通过id查找

    options = select.find_elements_by_tag_name("option")

    for option in options:

        if option.get_attribute("textContent").encode("utf-8") == value:

        option.click()

        break