Pythonic(OO) 方式根据对象类型选择类方法

Question

是否有更好的Pythonic/面向对象方法来选择在运行时执行哪个特定类方法，具体取决于对象的类型，因为使用 type() 方法不被认为优雅(?)

我为我正在使用的三种数据类型编写了以下代码。它基本上将不同的函数存储在字典中作为值，并将其与相应的对象类型作为键配对:

import pathlib
import _io

########################################
class choose_for :

    def __init__(self, var):
        func_dict = {str:self.func1, pathlib.WindowsPath:self.func2, _io.TextIOWrapper:self.func3}
        self.func = func_dict[type(var)]

    def func1(self) :
        print("Because it is for STRING like \n")

    def func2(self) :
        print("Because it is for PATH like \n")

    def func3(self) :
        print("Because it is for FILE_POINTER like \n")

    def execute(self):
        print("This object will be executed by : ", self.func)
        self.func()

########################################
var1 = str("something")

var2 = pathlib.Path()

var3 = _io.open("file.txt")

########################################
chosen1 = choose_for(var1)
chosen1.execute()

chosen2 = choose_for(var2)
chosen2.execute()

chosen3 = choose_for(var3)
chosen3.execute()

########################################
var3.close()

它给出以下输出:

This object will be executed by :  <bound method choose_for.func1 of <__main__.choose_for object at 0x0000020A150A3088>>
Because it is for STRING like

This object will be executed by :  <bound method choose_for.func2 of <__main__.choose_for object at 0x0000020A1509EFC8>>
Because it is for PATH like

This object will be executed by :  <bound method choose_for.func3 of <__main__.choose_for object at 0x0000020A15276B48>>
Because it is for FILE_POINTER like

对于我在这里想做的事情，还有什么技术术语吗？ 我认为这可能与单分派(dispatch)、函数重载或多态性有关，但我不确定。

Answer 1

这确实是 single-dispatch ，Python 通过 functools 模块支持。无需上课。

from functools import singledispatch


@singledispatch
def execute(arg):
    print(f"something with type {type(arg)}")

@execute.register(str):
def _(arg):
    print("Because it is for STRING like \n")

@execute.register(pathlib.Path):
def _(arg):
    print("Because it is for PATH like \n")

@execute.register(io.FileIO)
def _(arg):
    print("Because it is for FILE_POINTER like \n")

测试一下，你就会发现

>>> execute("something")
Because it is for STRING like
>>> execute(pathlib.Path())
Because it is for PATH like
>>> execute(_io.open("file.txt"))
Because it is for FILE_POINTER like
>>> execute(3)
something with type <class 'int'>

要对方法使用单次调度，请使用 singledispatchmethod，它将调度该方法的第二参数，跳过隐式提供的实例或类参数。