ValueError: too many values to unpack (expected 2)

class Mymeta(type):
    def __new__(cls, class_name, class_bases, class_attrs):
        print('--->', cls)  # ---> 
        print('--->', class_name)  # ---> Chinese
        print('--->', class_bases)  # ---> (,)
        print('--->', class_attrs)  # 'Chinese', 'country': 'china', 'skin': 'yello', '__init__': ....
        print(class_attrs.items())
        update_attrs = {}
        for key, value in class_attrs:
            if not callable(value) and not key.startswith('__'):
                update_attrs[key.upper()] = value
            else:
                update_attrs[key] = value

        return type.__new__(cls, class_name, class_bases, update_attrs)


class Chinese(object, metaclass=Mymeta):
    country = 'china'
    skin = 'yello'

 

返回了下面的错误:

    for key, value in class_attrs:
ValueError: too many values to unpack (expected 2)

原因是字典这个是一个迭代器对象,参考官方文档找到下列说明,字典只支持Key的遍历,,如果想对key,value,则可以使用items方法。
The “implicit” iteration that dictionaries support only iterates over keys.

python只支持对于key的遍历,所以不能使用for k,v这种形式,这个时候会提示ValueError: too many values to unpack,
正确代码如下:

for key, value in class_attrs.items():

转载于:https://www.cnblogs.com/lshedward/p/10082997.html

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