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.

让我们从以下开始:

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，我们将尝试创建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:

回溯(最近一次调用最后一次):第 13 行，在doer.doSomething() 第 9 行，调用打印%s 把它做得更好"% 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，我尝试将 callable 作为属性分配给对象实例并调用它:

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 就可以工作，但是当我这样做时，它会在 self.name 上给我一个名称错误，因为它引用了可调用的 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.

所以我正在寻找一种pythonic方式将匿名函数分配给类函数或实例方法，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

你的第一种方法没问题，你只需要将函数分配给类:

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，请参阅 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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