标签：object foo int func function 有用 名称空间 ini 代码
class Foo: pass print(Foo, type(Foo)) print(type, type(type)) ‘‘‘ <class ‘__main__.Foo‘> <class ‘type‘> <class ‘type‘> <class ‘type‘> ‘‘‘
Python中万物皆对象,所有用来创建对象的类,本身也对象,类是type类的对象
type类叫做元类,是所有元类的类
元类: 造类的类 -类的类
-- 控制类的产生
--控制类的对象的产生
在type的init方法中
def __init__(cls, what, bases=None, dict=None): # known special case of type.__init__ """ type(object_or_name, bases, dict) type(object) -> the object‘s type type(name, bases, dict) -> a new type # (copied from class doc) """ pass
type(name, bases, dict) -> a new type
name为类的名字 ‘C‘
bases为继承的基类 (object,)
dict为名称空间 {}
class Foo: pass print(Foo, type(Foo)) C = type(‘C‘, (object,), {}) print(C, type(C)) C.name = 123 print(C.name)
‘‘‘
<class ‘__main__.Foo‘> <class ‘type‘>
<class ‘__main__.C‘> <class ‘type‘>
123
‘‘‘
由此可见使用type可以直接创建一个类
使用exec给类创建名称空间
s = ‘‘‘ my_a = 10 my_b = 20 def __init__(self, name): self.name = name @classmethod def print_msg(cls,msg): print(msg) ‘‘‘ dic = {} exec(s, {}, dic) C = type(‘C‘, (object,), dic) print(C, type(C)) print(C.__dict__) # C() # 报错 __init__中带有一个参数 C(‘yyf‘) # 不报错 C.print_msg(123)
‘‘‘
<class ‘__main__.C‘> <class ‘type‘>
{‘my_a‘: 10, ‘my_b‘: 20, ‘__init__‘: <function __init__ at 0x01AA0858>, ‘print_msg‘: <classmethod object at 0x01AD9950>, ‘__module__‘: ‘__main__‘, ‘__dict__‘: <att ribute ‘__dict__‘ of ‘C‘ objects>, ‘__weakref__‘: <attribute ‘__weakref__‘ of ‘C‘ objects>, ‘__doc__‘: None}
123
‘‘‘
标签：object foo int func function 有用 名称空间 ini 代码
原文地址：https://www.cnblogs.com/yuyafeng/p/10957404.html
