Python:展平对象列表 [英] Python: Flatten a list of Objects

问题描述

我有一个对象列表，每个对象内部都有其他对象类型的列表.我想提取这些列表并创建其他对象的新列表.

I have a list of Objects and each object has inside it a list of other object type. I want to extract those lists and create a new list of the other object.

List1:[Obj1, Obj2, Obj3]

Obj1.myList = [O1, O2, O3]
Obj2.myList = [O4, O5, O6]
Obj3.myList = [O7, O8, O9]

我需要这个:

L = [O1, O2, O3, O4, ...., O9];

我尝试了extend()和reduce()，但是没有用

I tried extend() and reduce() but didn't work

bigList = reduce(lambda acc, slice: acc.extend(slice.coresetPoints.points), self.stack, [])

P.S.

寻找python展平列表的列表并没有帮助，因为我得到了其他对象的列表.

Looking for python flatten a list of list didn't help as I got a list of lists of other object.

推荐答案

使用itertools.chain(或者在这种情况下更好，如niemmi所说的itertools.chain.from_iterable)，避免创建临时列表并使用extend

using itertools.chain (or even better in that case itertools.chain.from_iterable as niemmi noted) which avoids creating temporary lists and using extend

import itertools
print(list(itertools.chain(*(x.myList for x in List1))))

或(清晰得多，速度更快):

or (much clearer and slightly faster):

print(list(itertools.chain.from_iterable(x.myList for x in List1)))

小型可复制测试:

class O:
    def __init__(self):
        pass

Obj1,Obj2,Obj3 = [O() for _ in range(3)]

List1 = [Obj1, Obj2, Obj3]

Obj1.myList = [1, 2, 3]
Obj2.myList = [4, 5, 6]
Obj3.myList = [7, 8, 9]

import itertools
print(list(itertools.chain.from_iterable(x.myList for x in List1)))

结果:

[1, 2, 3, 4, 5, 6, 7, 8, 9]

(用于平整列表清单的所有食谱:

(all recipes to flatten a list of lists: How to make a flat list out of list of lists?)

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