面向对象之元类等相关内容-34
# 一切源自于一句话：python中一切皆为对象
# 一：元类介绍
"""
# 元类=》OldboyTeacher类=》obj
class OldboyTeacher(object):
school = 'oldboy'
def __init__(self, name, age):
self.name = name
self.age = age
def say(self):
print('%s says welcome to the oldboy to learn Python' % self.name)
obj = OldboyTeacher('egon', 18) # 调用OldboyTeacher类=》对象obj
# 调用元类=》OldboyTeacher类
# print(type(obj))
print(type(OldboyTeacher))
# 结论：默认的元类是type，默认情况下我们用class关键字定义的类都是由type产生的
"""
# 二：class关键字底层的做了哪些事
'''
# 1、先拿到一个类名
class_name = "OldboyTeacher"
# 2、然后拿到类的父类
class_bases = (object,)
# 3、再运行类体代码，将产生的名字放到名称空间中
class_dic = {}
class_body = """
school = 'oldboy'
def __init__(self, name, age):
self.name = name
self.age = age
def say(self):
print('%s says welcome to the oldboy to learn Python' % self.name)
"""
exec(class_body,{},class_dic)
exec方法是将类体代码转换成字典的形式 参数为 类体代码、空字典、需要导出的字典
# print(class_dic)
# 4、调用元类（传入类的三大要素：类名、基类、类的名称空间）得到一个元类的对象，然后将元类的对象赋值给变量名OldboyTeacher,oldboyTeacher就是我们用class自定义的那个类
OldboyTeacher = type(class_name,class_bases,class_dic)
'''
# 三：自定义元类
'''
class Mymeta(type): # 只有继承了type类的类才是自定义的元类
pass
class OldboyTeacher(object, metaclass=Mymeta):
school = 'oldboy'
def __init__(self, name, age):
self.name = name
self.age = age
def say(self):
print('%s says welcome to the oldboy to learn Python' % self.name)
# 1、先拿到一个类名:"OldboyTeacher"
# 2、然后拿到类的父类:(object,)
# 3、再运行类体代码，将产生的名字放到名称空间中{...}
# 4、调用元类（传入类的三大要素：类名、基类、类的名称空间）得到一个元类的对象，然后将元类的对象赋值给变量名OldboyTeacher,oldboyTeacher就是我们用class自定义的那个类
OldboyTeacher = Mymeta("OldboyTeacher",(object,),{...})
'''
# 四：自定义元类来控制OldboyTeacher类的产生
'''
import re
class Mymeta(type): # 只有继承了type类的类才是自定义的元类
def __init__(self, class_name, class_bases, class_dic):
# print(self) # 类<class '__main__.OldboyTeacher'>
# print(class_name)
# print(class_bases)
# print(class_dic)
if not re.match("[A-Z]", class_name):
raise BaseException("类名必须用驼峰体")
if len(class_bases) == 0:
raise BaseException("至少继承一个父类")
# print("文档注释：",class_dic.get('__doc__'))
doc=class_dic.get('__doc__')
if not (doc and len(doc.strip()) > 0):
raise BaseException("必须要有文件注释，并且注释内容不为空")
# OldboyTeacher = Mymeta("OldboyTeacher",(object,),{...})
class OldboyTeacher(object,metaclass=Mymeta):
"""
adsaf
"""
school = 'oldboy'
def __init__(self, name, age):
self.name = name
self.age = age
def say(self):
print('%s says welcome to the oldboy to learn Python' % self.name)
'''
# 五：自定义元类来控制OldboyTeacher类的调用
'''
import re