metaframe 1.0.1

metaframe

metaframe元类基础设施，用于拦截实例创建/初始化，允许修改args/kwargs和实例。

文档

在readthedocs.org上阅读完整文档

• metaframe文档

Python 2/3支持

• Python 2.7

• Python 3.2/3.3/3.4/3.5

• 它还可以与pypy和pypy3一起工作

安装

metaframe是自包含的，没有外部依赖项

从PyPI安装

pip install metaframe

从源代码安装

• 将源代码中找到的目录放置在您的项目内

功能

• MetaFrame元类适用于任何对象 - 嵌入静态方法_with_class以启用继承

• MetaFrameBase类，类可以从它继承

• 3个钩子（类方法）

  • _new_pre：在对象创建之前调用

  • _new_do：用于对象创建

  • _init_pre：在对象创建/初始化之前调用

  • _init_do：用于对象初始化

  • _init_post：在对象初始化之后调用

用法

一个快速示例，在对象创建之前从kwargs中过滤掉None和不能转换为float的参数

from metaframe import MetaFrame


class A(MetaFrame.as_metaclass(object)):

    @classmethod
    def _new_do(cls, *args, **kwargs):

        nkwargs = dict()
        for key, val in kwargs.items():

            # Remove any argument with a value of None
            if val is None:
                continue

            try:
                val = float(val)
            except:
                continue

            nkwargs[key] = val

        # The only nuisance being the cumbersome call to _new_do
        # super doesn't work
        obj, args, kwargs = cls.__class__._new_do(cls, *args, **nkwargs)
        return obj, args, kwargs

    def __init__(self, **kwargs):
        for key, val in kwargs.items():
            print('key, val, type', key, val, type(val))


a = A(p1=72, p2=None, p3='hello', p4=None, p5='72.5')


# Now with a subclassed MetaB from MetaFrame
# Here super can be applied to find the higher in the hierarchy _new_do

class MetaB(MetaFrame):

    def _new_do(cls, *args, **kwargs):

        nkwargs = dict()
        for key, val in kwargs.items():

            # Remove any argument with a value of None
            if val is None:
                continue

            try:
                val = float(val)
            except:
                continue

            nkwargs[key] = val

        # super can be called directly
        obj, args, kwargs = super(MetaB, cls)._new_do(*args, **nkwargs)
        return obj, args, kwargs


class B(MetaB.as_metaclass()):
    def __init__(self, **kwargs):
        for key, val in kwargs.items():
            print('key, val, type', key, val, type(val))


b = B(p1=27, p2=None, p3='olleh', p4=None, p5='5.27')