这篇文章给大家分享的是有关python怎么创建和使用一个简单的元类的内容。小编觉得挺实用的，因此分享给大家做个参考，一起跟随小编过来看看吧。
网站建设哪家好，找
成都创新互联！专注于网页设计、网站建设、微信开发、
小程序定制开发、集团企业网站建设等服务项目。为回馈新老客户创新互联还提供了
连云港免费建站欢迎大家使用！
示例
#!/usr/bin/env python
# [SNIPPET_NAME: Simple metaclass]
# [SNIPPET_CATEGORIES: Python Core]
# [SNIPPET_DESCRIPTION: Shows how to create a and use a simple metaclass]
# [SNIPPET_AUTHOR: Florian Diesch ]
# [SNIPPET_LICENSE: MIT]
# Copyright 2010 Florian Diesch
# All rights reserved.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
class PropertyMetaclass(type):
"""
This metaclass expects its instances to have a class attribute
__properties__ that is a dict mapping property names to their
default values. The metaclass creates the corresponding
properties
"""
def __init__(cls, name, bases, dict):
type.__init__(cls, name, bases, dict)
props = getattr(cls, '__properties__', {})
for name, default in props.iteritems():
type(cls).create_property(cls, name, default)
def attr_name(cls, prop):
""" returns the attribute name for property """
return '_%s'%prop
def create_property(cls, name, default):
""" creates a property named with default value """
getter=cls.create_getter(name)
setter=cls.create_setter(name)
prop=property(getter, setter, None, None)
# that's the attribute holding the actual value
setattr(cls, cls.attr_name(name), default)
# that's the property
setattr(cls, name, prop)
def create_getter(cls, prop):
""" creates a getter method for property """
attr=cls.attr_name(prop)
def getter(self):
print " class %s: get %s"%(cls.__name__, prop)
return getattr(self, attr)
return getter
def create_setter(cls, prop):
""" creates a setter method for property """
attr=cls.attr_name(prop)
def setter(self, value):
print " class %s: set %s to '%s'"%(cls.__name__, prop, value)
setattr(self, attr, value)
return setter
class Book(object):
__metaclass__= PropertyMetaclass # use the metaclass
__properties__ = { # some properties
'author': '[unknown title]',
'title': '[unknown author]'
}
if __name__ == '__main__':
book = Book()
print '%s by %s'%(book.title, book.author)
book.author = 'Euclid'
book.title = 'Elements'
print '%s by %s'%(book.title, book.author)
# prints:
#
# class Book: get title
# class Book: get author
# --unknown author-- by --unknown title--
# class Book: set author to 'Euclid'
# class Book: set title to 'Elements'
# class Book: get title
# class Book: get author
# Elements by Euclid
感谢各位的阅读！关于“python怎么创建和使用一个简单的元类”这篇文章就分享到这里了，希望以上内容可以对大家有一定的帮助，让大家可以学到更多知识，如果觉得文章不错，可以把它分享出去让更多的人看到吧！
另外有需要云服务器可以了解下创新互联cdcxhl.cn，海内外云服务器15元起步，三天无理由+7*72小时售后在线，公司持有idc许可证，提供“云服务器、裸金属服务器、高防服务器、香港服务器、美国服务器、虚拟主机、免备案服务器”等云主机租用服务以及企业上云的综合解决方案，具有“安全稳定、简单易用、服务可用性高、性价比高”等特点与优势，专为企业上云打造定制，能够满足用户丰富、多元化的应用场景需求。
网页标题：python怎么创建和使用一个简单的元类-创新互联
文章URL：
http://cdxtjz.com/article/diddoj.html
