Metadata in Django

The meta class in Django is confused when it looks at the Form-related source code of Django (1.6), so django is excerpted. forms. forms. several code snippets in py are used to analyze how the metadata class is used in Django:

def with_metaclass(meta, *bases):    """Create a base class with a metaclass."""    return meta("NewBase", bases, {}) class DeclarativeFieldsMetaclass(type):    def __new__(cls, name, bases, attrs):        print('cls: %s, name: %s, bases: %s ,attrs: %s\n' % (cls, name, bases, attrs))         new_class = super(DeclarativeFieldsMetaclass, cls).__new__(cls, name, bases, attrs)#        new_class._meta = '123'        return new_class class BaseForm(object):    pass class Form(with_metaclass(DeclarativeFieldsMetaclass, BaseForm)):    pass     class MyForm(Form):    a = 1    b = 2

Load the Python module above, and the console will output:

Cls: , Name: NewBase, bases :( ,), Attrs :{}

Cls: , Name: Form, bases :( ,), Attrs: {'_ module _': '_ main __'}

Cls: , Name: MyForm, bases :( ,), Attrs: {'a': 1, '_ module _': '_ main _', 'B': 2}

Although metaclass is not directly specified for MyForm in code, because MyForm inherits from Form, and Form inherits from the class "NewBase" generated by DeclarativeFieldsMetaclass, DeclarativeFieldsMetaclass is actually the metaclass of MyForm.