Python 3.8 Walrus 运算符，不带多个变量并赋值

Question

我正在研究硒包装器。我想检查网页上的元素是否可见。selector该函数获取遵循模式的输入变量，"selector=value"例如"id=content"，但也可以是 this "link_text=Hello World"。搜索函数将该字符串拆分为两个部分以搜索实际元素并将其返回以供错误处理使用。异常消息应说明选择器和值：

class KeywordFailed(Exception):
    
    def __init__(self, message):
        self.message = message
        super().__init__(self.message)

class ElementFoundButNotVisible(KeywordFailed):
    def __init__(self, element, selector):
        super().__init__("element: \"" + element + "\" with selector: \"" + selector + "\" is not visible")

class DefaultKeywords:

    browser = webdriver.Firefox()

    def selectElement(self, selector):
        selectorValue = selector.split("=")[1]
        selector = selector.split("=")[0]
        try:
            if selector == "id":
                element = self.browser.find_element_by_id(selectorValue)
            elif selector == "xpath":
                element = self.browser.find_element_by_xpath(selectorValue)
            elif selector == "link_text":
                element = self.browser.find_element_by_link_text(selectorValue)
            elif selector == "partial_link_text":
                element = self.browser.find_element_by_partial_link_text(selectorValue)
            elif selector == "name":
                element = self.browser.find_element_by_name(selectorValue)
            elif selector == "class_name":
                element = self.browser.find_element_by_class_name(selectorValue)
            elif selector == "css_selector":
                element = self.browser.find_element_by_css_selector(selectorValue)
            elif selector == "tag":
                element = self.browser.find_element_by_tag_name(selectorValue)
        except NoSuchElementException:
            raise ElementNotFound(selectorValue, selector)
        else:
            return element, selector

    def findAndCheckIfVisible(self, selector):
        if (value, selector) := not self.selectElement(selector).is_displayed():
            raise ElementFoundButNotVisible(element, selector)
...

执行时，我收到以下错误：

SyntaxError: cannot use assignment expressions with tuple

我可以将分离过程移至其自己的函数中，然后在异常和搜索函数中将其称为一个函数，但我真的不想这样做，因为这意味着我要执行相同的代码两次。

Answer 1

您不能使用带有赋值表达式的解包形式。相反，请考虑使用赋值表达式为返回的元组创建名称，然后从表达式中的名称解包：

def findAndCheckIfVisible(self, selector):
   if not (result:=self.selectElement(selector).is_displayed()):
      raise ElementFoundButNotVisible(element, selector)
   value, selector = result

另外，不要考虑使用每种选择器类型的显式条件getattr：

try:
   element = getattr(self.browser, f'find_element_by_{selector}')(selectorValue)
except NoSuchElementException:
   pass