12 隐式等待，显示等待

def wait_for_row_in_list_table(self,row_text):
        start_time = time.time()
        while True:
            try:
                table = self.browser.find_element_by_id('id_list_table')
                rows = table.find_elements_by_tag_name('tr')
                self.assertIn(row_text,[row.text for row in rows])
                return
            except(AssertionError,WebDriverException)as e:
                if time.time() - start_time > MAX_WAIT:
                    raise e
                time.sleep(0.5)

python 之禅“明了胜于晦涩”，首选显示等待，selenium中的隐式等待在不同浏览器实现各不相同。selenium3的隐式等待在firefox驱动上极度不可靠