Walrus Operator: NameError: free variable 'it' referenced before assignment in enclosing scope

Question

我想像这样使用海象运算符创建一个列表：

    myvar = tr_list[8].css('td ::text').extract()
    item['myvar'] = [
        it := re.sub(PATTERN, "", i).strip() for i in myvar if len(it) > 0
    ]

我得到这个错误：

    it := re.sub(PATTERN, "", i).strip() for i in myvar if len(it) > 0
NameError: free variable 'it' referenced before assignment in enclosing scope

另一方面，当我这样做时它起作用了：

    myvar = tr_list[8].css('td ::text').extract()
    item['myvar'] = [
        re.sub(PATTERN, "", i).strip() for i in myvar if len(re.sub(PATTERN, "", i).strip()) > 0
    ]

其中：

PATTERN = "\r|\t|\n"

有人可以帮忙吗？我不知道我在这里错过了什么

Answer 1

好的。我想我终于通过将其更改为解决了它：

    myvar = tr_list[8].css('td ::text').extract()
    item['myvar'] = [
        n for i in myvar if len(n := re.sub(PATTERN, "", i).strip()) > 0
    ]

Walrus Operator: NameError: free variable 'it' referenced before assignment in enclosing scope

Walrus Operator: NameError: free variable 'it' referenced before assignment in enclosing scope

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