Python:如何循环变化深度的列表? [英] Python: How to loop a list of lists of varying depth?

问题描述

我有一个像这样的数据结构(列表的实际列表很长且深度不同).我确实知道他们的深度.

I have a data structure like this (the actual lists of lists are very long and of varying depth). I do know their depth beforehand.

 a=( [1,2], [2,3,[4,5]] )
 b=( [[1,2],[2,3]] )

一个要遍历每个列表的地方.如何做到最好?

A want to loop through each single list. How to best do this?

我不想最终做这样的事情:

I don't want to end up doing something like this:

for l in a:
    if instance(l, list):
        for ll in l:
            if instance(ll, list): 
                ...

推荐答案

由于您未定义目的，因此我正在编写一个对所有元素求和的函数:

Since you don't defined the purpose, i'm coding a function that sum all elements:

def rec_sum(lst):
    if not lst:
        return 0
    el = lst.pop()
    if isinstance(el, list):
        return rec_sum(el) + rec_sum(lst)
    else:
        return el + rec_sum(lst)

即使您事先知道深度，使用递归也更容易解决.

Even if you know the depth beforehand, it's easier to solve using recursion.

请记住，Python限制堆叠的1000个堆栈帧.因此，如果您的列表中包含1000多个项目，则应该获得Exception.

Remember that Python limits 1000 stack frames stacked. So, if your list have more than 1000 items, you should get an Exception.

如果您认为可以有1000多个项目，那么这里是一个混合解决方案，它使用递归和for循环.它被限制为1000个级别，而不是1000个项目:

If you think you can have more than 1000 items, here it is a mixed solution, that uses recursion and for loops. It is limited into 1000 levels, instead of 1000 items:

def rec_for_sum(lst):
    if not lst:
        return 0
    count = 0
    for el in lst:
        if not isinstance(el, list):
            count += el
        else:
            count += rec_for_sum(el)
    return count

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