python的type函数

对于type，经常会用到的是判断类型，但是判断类型更推荐的一种方式是使用isinstance();但是很少会用到type的另外一个功能，生成一个新的类型，看官方解释：

class type(name, bases, dict)
With three arguments, return a new type object. This is essentially a dynamic form of the class statement. The name string is the class name and becomes the name attribute; the bases tuple itemizes the base classes and becomes the bases attribute; and the dict dictionary is the namespace containing definitions for class body and becomes the dict attribute. For example, the following two statements create identical type objects:

>>> class X(object):
...     a = 1
...
>>> X = type('X', (object,), dict(a=1))

这样就可以产生一个新的类型X。

再举个demo：
django框架中的BaseManager

    @classmethod
    def from_queryset(cls, queryset_class, class_name=None):
        if class_name is None:
            class_name = '%sFrom%s' % (cls.__name__, queryset_class.__name__)
        class_dict = {
            '_queryset_class': queryset_class,
        }
        class_dict.update(cls._get_queryset_methods(queryset_class))
        return type(class_name, (cls,), class_dict)

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