[Python3 填坑] 018 组装类的几个例子

目录

• 1. print( 坑的信息 )
• 2. 开始填坑
  • 2.1 MetaClass 举例
  • 2.2 type 举例
  • 2.3 MetaClass 举例

---

1. print( 坑的信息 )

• 挖坑时间：2019/04/07
• 明细

坑的编码	内容
Py024-2	MethodType 举例
Py024-3	type 举例
Py024-4	MetaClass 举例

---

2. 开始填坑

2.1 MetaClass 举例

from types import MethodType
class A():
    pass
def say(self):
    print("this is say()")
a = A()
a.say = MethodType(say, A)
a.say()

>>>

this is say()

2.2 type 举例

# 1. 定义类应该具有的成员函数
def say(self):
    print("this is say()")
def eat(self):
    print("this is eat()")
# 2. 用 type 来创建一个类
A = type( "AName", (object, ), {"class_say":say, "class_eat":eat})
# 3. 像正常访问一样使用类
a = A()
a.class_say()
a.class_eat()

>>>

this is say()

this is eat()

2.3 MetaClass 举例

# 元类写法是固定的，必须继承自 type
# 元类一般命名以 MetaClass 结尾
class ExampleMetaClass(type):
    def __new__(cls, region, gender, attrs):
        print("this is MetaClass")
        attrs['id_num'] = '9527'
        attrs['age'] = "18"
        return type.__new__(cls, region, gender, attrs)
# 元类定义完就可以使用
class Person(object, metaclass=ExampleMetaClass):
    pass
york = Person()
print(york.id_num)

>>>

this is MetaClass

9527