制作可以带有列表或任意数量参数的函数的最佳方法? [英] Best way to make a function which can take a list or any number of arguments?

问题描述

实现for_each函数的正确方法是什么，以便它可以采用任意数量的参数，列表或元组作为参数?

What's the correct way of implementing the for_each function so that it can take any number of argument or a list or a tuple as parameter?

def do_something(arg):
    print("done", arg)


def for_each(func, *args):
    if len(args) == 1:  # How to do this, since this gives an
        args = args[0]  # error if there's only one parameter besides func?
    for arg in args:
        func(arg)


for_each(do_something, 1, 2)
for_each(do_something, ['foo', 'bar'])
for_each(do_something, (3, 4, 5))

输出:

done 1
done 2
done foo
done bar
done 3
done 4
done 5

实现此目标的正确方法是什么?因为这样调用会破裂:

What's the correct way to achieve this? Since this will break if called like this:

for_each(do_something, 1)

Traceback (most recent call last):
  File "main.py", line 12, in <module>
    for_each(do_something, 1)
  File "main.py", line 8, in for_each
    for arg in args:
TypeError: 'int' object is not iterable

推荐答案

您要检查您的第一个元素是列表还是元组，如下所示:

You want to check if your first element is a list or a tuple like this:

(您需要检查实例，以防用户仅使用一个int实例，否则您的代码将失败)

(You need to check the instance, in case user just use a single int for instance, your code would fail)

def for_each(func, *args):
  if len(args) == 1 and (isinstance(args[0], tuple) or isinstance(args[0], list)): # You can even check on Iterable by importing collections.abc.Iterable
    args = args[0]
  for arg in args:
    func(arg)

但是，您可以走得更远，让用户输入几个Iterable，而不仅仅是元组或列表，例如:

However, you can go further and let the user input several Iterable and not only tuples or lists, such as follow :

from collections.abc import Iterable
from itertools import chain


def do_something(arg):
    print("done", arg)

def for_each(func, *args):
  if all(map(lambda x: isinstance(x, Iterable), args)) and not any(map(lambda x: isinstance(x, str), args)):
    args = chain(*args)
  for arg in args:
    func(arg)


for_each(do_something, [0, 1], [0, 2])

这篇关于制作可以带有列表或任意数量参数的函数的最佳方法?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！