在Python中动态分配函数实现 [英] Dynamically assigning function implementation in Python

问题描述

我想动态分配一个函数实现。

I want to assign a function implementation dynamically.

让我们从以下内容开始：

Let's start with the following:

class Doer(object):

    def __init__(self):
        self.name = "Bob"

    def doSomething(self):
        print "%s got it done" % self.name

def doItBetter(self):
    print "Done better"

在其他语言中，我们会将doItBetter设为匿名函数并将其分配给对象。但是不支持Python中的匿名函数。相反，我们将尝试制作一个可调用的类实例，并将其分配给该类：

In other languages we would make doItBetter an anonymous function and assign it to the object. But no support for anonymous functions in Python. Instead, we'll try making a callable class instance, and assign that to the class:

class Doer(object):

    def __init__(self):
        self.name = "Bob"

class DoItBetter(object):

    def __call__(self):
        print "%s got it done better" % self.name

Doer.doSomething = DoItBetter()
doer = Doer()
doer.doSomething()

这给了我这个：

跟踪（最近一次通话最后一次）：第13行，在
doer.doSomething（）第9行，在通话中
打印％s效果更好％self.name AttributeError：'DoItBetter'对象没有属性'name'

Traceback (most recent call last): Line 13, in doer.doSomething() Line 9, in call print "%s got it done better" % self.name AttributeError: 'DoItBetter' object has no attribute 'name'

最后，我尝试分配可调用对象以对象属性作为属性并调用它：

Finally, I tried assigning the callable to the object instance as an attribute and calling it:

class Doer(object):

    def __init__(self):
        self.name = "Bob"

class DoItBetter(object):

    def __call__(self):
        print "%s got it done better" % self.name


doer = Doer()
doer.doSomething = DoItBetter()
doer.doSomething()

只要我不在DoItBetter中引用self，它就可以工作，但是当我这样做时，在 self.name 上给我一个名称错误，因为它引用了可调用对象的 self ，而不是拥有类 self 。

This DOES work as long as I don't reference self in DoItBetter, but when I do it gives me an name error on self.name because it's referencing the callable's self, not the owning class self.

所以我我正在寻找一种将匿名函数分配给类函数或实例方法的pythonic方法，其中方法调用可以引用对象的 self 。

So I'm looking for a pythonic way to assign an anonymous function to a class function or instance method, where the method call can reference the object's self.

推荐答案

您的第一种方法是好的，您只需要将该函数分配给该类：

Your first approach was OK, you just have to assign the function to the class:

class Doer(object):
    def __init__(self):
        self.name = "Bob"

    def doSomething(self):
        print "%s got it done" % self.name

def doItBetter(self):
    print "%s got it done better" % self.name

Doer.doSomething = doItBetter

匿名函数与此无关（顺便说一句，Python支持由单个表达式组成的简单匿名函数，请参见 lambda ）。

Anonymous functions have nothing to do with this (by the way, Python supports simple anonymous functions consisting of single expressions, see lambda).

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