Question

基本上，我想创建一个带有staticmethods的“模板”类型对象，然后创建一个继承自它的新对象，但使用父项的方法使用functools.partial，其中子项的参数是用过的。子对象的参数与父对象的参数具有相同的名称。由此产生的范例将是这样的：

class Naked:

    @staticmethod        
    def echo1(foo):
        return f"echo1: {foo}"

    @staticmethod        
    def echo2(bar, bla):
        return f"echo2: {bar}, {bla}"

class Clothed(Naked):
    def __init__(self, *args, **kwargs):
        for arg in args:
            setattr(self, arg, arg)

        for k,v in kwargs.items():
            setattr(self, k, v)

a = Clothed(foo = "Hello", bar = "World")
a.echo1 == "echo1: Hello"
a.echo2("wsup?") == "echo2: World, wsup?"

以下尝试不起作用：

from inspect import signature
from functools import partial
class Meta(type):
    def __init__(cls, name, bases, attrs):
         funcs = (k for k,v in attrs.items() if callable(v) and k not in dir(type)) #this doesn't work...
         for func in funcs:
            args = signature(func).keys() #function argument names
            newargs = {arg:getattr(self, arg, None) for arg in args} #create dictionary with val from instance, how is this possible, no self here?
            attrs[func] = partial(func,newargs)
        return type.__init__(cls, name, bases, attrs)  

class Naked(metaclass=Meta):

    @staticmethod        
    def echo1(foo):
        return f"echo1: {foo}"

    @staticmethod        
    def echo2(bar, bla):
        return f"echo2: {bar}, {bla}"

class Clothed(Naked):
    def __init__(self, *args, **kwargs):
        for arg in args:
            setattr(self, arg, arg)

        for k,v in kwargs.items():
            setattr(self, k, v)

Answer 1

我不知道如何使用元类进行此操作，但这是使用mixin类的可能解决方案。你可以使用这样的东西。

from inspect import signature
from functools import partialmethod, partial

class Naked:

    @staticmethod        
    def echo1(foo):
        return f"echo1: {foo}"

    @staticmethod        
    def echo2(bla, bar):
        return f"echo2: {bar}, {bla}"

class PartialMixin:
    def __init__(self, **kwargs):
        methods = [m for m in dir(self) if callable(getattr(self, m)) and m not in dir(type)]
        for method_name in methods:
            method = getattr(self, method_name)
            method_kwargs = signature(method).parameters.keys()
            partial_kwargs = {k:kwargs[k] for k in kwargs if k in method_kwargs}
            new_method = partial(method, **partial_kwargs)
            # if the methods are not static, maybe functools.partialmethod should be used.
            setattr(self, method_name, new_method)

class Clothed(PartialMixin, Naked):
    pass

a = Clothed(foo = "Hello", bar = "World")
a.echo1() == "echo1: Hello"
a.echo2("wsup?") == "echo2: World, wsup?"

Python魔术元类创建

1 个答案: