相关疑难解决方法(0)

考虑这个小例子:

import datetime as dt

class Timed(object):
    def __init__(self, f):
        self.func = f

    def __call__(self, *args, **kwargs):
        start = dt.datetime.now()
        ret = self.func(*args, **kwargs)
        time = dt.datetime.now() - start
        ret["time"] = time
        return ret

class Test(object):
    def __init__(self):
        super(Test, self).__init__()

    @Timed
    def decorated(self, *args, **kwargs):
        print(self)
        print(args)
        print(kwargs)
        return dict()

    def call_deco(self):
        self.decorated("Hello", world="World")

if __name__ == "__main__":
    t = Test()
    ret = t.call_deco()

打印

Hello
()
{'world': 'World'}

为什么self参数(应该是Test obj实例)不作为第一个参数传递给装饰函数decorated？

如果我手动完成,例如:

def call_deco(self):
    self.decorated(self, "Hello", …

假设我们有一个类'Parent',由于某种原因已__new__定义,并且继承了它的类'Child'.(在我的情况下,我试图继承我无法修改的第三方课程)

class Parent:
    def __new__(cls, arg):
        # ... something important is done here with arg

我的尝试是:

class Child(Parent):
    def __init__(self, myArg, argForSuperclass):
         Parent.__new__(argForSuperclass)
         self.field = myArg

但同时

p = Parent("argForSuperclass")

按预期工作

c = Child("myArg", "argForSuperclass")

失败,因为'Child'试图调用__new__它从'Parent'而不是它自己的__init__方法继承的方法.

为了获得预期的行为,我必须在"儿童"中进行哪些更改？

最近,StackOverflow社区帮助我开发了一个相当简洁的@memoize装饰器,它不仅能够以一般方式装饰函数,还能够装饰方法和类,即,无需预先知道它将装饰什么类型的东西.

我遇到的一个问题是,如果你用一个类装饰一个类@memoize,然后尝试用它来装饰其中一个方法@staticmethod,这将无法按预期工作,即你根本无法调用ClassName.thestaticmethod().我提出的原始解决方案看起来像这样:

def memoize(obj):
    """General-purpose cache for classes, methods, and functions."""
    cache = obj.cache = {}

    def memoizer(*args, **kwargs):
        """Do cache lookups and populate the cache in the case of misses."""
        key = args[0] if len(args) is 1 else args
        if key not in cache:
            cache[key] = obj(*args, **kwargs)
        return cache[key]

    # Make the memoizer func masquerade as the object we are memoizing.
    # This makes class attributes and static methods behave …