在python的List中通过其成员查找对象 [英] Find object by its member inside a List in python

问题描述

让我们假设以下简单对象:

lets assume the following simple Object:

class Mock:
    def __init__(self, name, age):
        self.name = name
        self.age = age

然后我有一个列表，其中包含一些像这样的对象:

then I have a list with some Objects like this:

myList = [Mock("Dan", 34), Mock("Jack", 30), Mock("Oli", 23)...]

是否有一些内置功能可以让我获得所有年龄为 30 岁的 Mocks?当然我可以遍历他们并比较他们的年龄，但是像

Is there some built-in feature where I can get all Mocks with an age of ie 30? Of course I can iterate myself over them and compare their ages, but something like

find(myList, age=30)

会很好.有这样的吗?

推荐答案

您可能希望对它们进行预索引 -

You might want to pre-index them -

from collections import defaultdict

class Mock(object):
    age_index = defaultdict(list)

    def __init__(self, name, age):
        self.name = name
        self.age = age
        Mock.age_index[age].append(self)

    @classmethod
    def find_by_age(cls, age):
        return Mock.age_index[age]

一张图片胜过千言万语:

a picture is worth a thousand words:

X 轴是 myList 中的 Mocks 数量，Y 轴是运行时间，以秒为单位.

X axis is number of Mocks in myList, Y axis is runtime in seconds.

• 红点是@dcrooney 的 filter() 方法
• 蓝点是@marshall.ward 的列表理解
• 隐藏在 X 轴后面的绿点是我的索引 ;-)

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