Python 如何在列表中查找重复项，并对找到的每个重复项实例执行不同的计算？

我想在

列表上迭代并找到重复项。如果发现重复项，我想对该重复项进行计算。如果发现同一实例的另一个副本，则应执行不同的计算

例如：

开始迭代列表

：

a_list = [1, 2, 3, 1, 2, 3, 1, 2, 3]

继续迭代

1, 2, 3, 1 [Instance of duplicate 1 found - Perform 1+1 on instance]

1, 2, 3, 1, 2 [Instance of duplicate 2 found - Perform 2+2 on instance]

1, 2, 3, 1, 2, 3 [Instance of duplicate 3 found - Perform 3+3 on instance]

1, 2, 3, 1, 2, 3, 1 [Second instance of duplicate 1 found - Perform 1+1+1 on instance]

1, 2, 3, 1, 2, 3, 1, 2 [Second instance of duplicate 2 found - Perform 2+2+2 on instance]

继续迭代

1, 2, 3, 1 [Instance of duplicate 1 found - Perform 1+1 on instance]

1, 2, 3, 1, 2 [Instance of duplicate 2 found - Perform 2+2 on instance]

1, 2, 3, 1, 2, 3 [Instance of duplicate 3 found - Perform 3+3 on instance]

1, 2, 3, 1, 2, 3, 1 [Second instance of duplicate 1 found - Perform 1+1+1 on instance]

1, 2, 3, 1, 2, 3, 1, 2 [Second instance of duplicate 2 found - Perform 2+2+2 on instance]

继续迭代

1, 2, 3, 1 [Instance of duplicate 1 found - Perform 1+1 on instance]

1, 2, 3, 1, 2 [Instance of duplicate 2 found - Perform 2+2 on instance]

1, 2, 3, 1, 2, 3 [Instance of duplicate 3 found - Perform 3+3 on instance]

1, 2, 3, 1, 2, 3, 1 [Second instance of duplicate 1 found - Perform 1+1+1 on instance]

1, 2, 3, 1, 2, 3, 1, 2 [Second instance of duplicate 2 found - Perform 2+2+2 on instance]

继续迭代

1, 2, 3, 1 [Instance of duplicate 1 found - Perform 1+1 on instance]

1, 2, 3, 1, 2 [Instance of duplicate 2 found - Perform 2+2 on instance]

1, 2, 3, 1, 2, 3 [Instance of duplicate 3 found - Perform 3+3 on instance]

1, 2, 3, 1, 2, 3, 1 [Second instance of duplicate 1 found - Perform 1+1+1 on instance]

1, 2, 3, 1, 2, 3, 1, 2 [Second instance of duplicate 2 found - Perform 2+2+2 on instance]

继续迭代

1, 2, 3, 1 [Instance of duplicate 1 found - Perform 1+1 on instance]

1, 2, 3, 1, 2 [Instance of duplicate 2 found - Perform 2+2 on instance]

1, 2, 3, 1, 2, 3 [Instance of duplicate 3 found - Perform 3+3 on instance]

1, 2, 3, 1, 2, 3, 1 [Second instance of duplicate 1 found - Perform 1+1+1 on instance]

1, 2, 3, 1, 2, 3, 1, 2 [Second instance of duplicate 2 found - Perform 2+2+2 on instance]

完成后，将创建一个包含所有计算的新列表：

1, 2, 3, 1, 2, 3, 1, 2, 3 [Second instance of duplicate 3 found - Perform 3+3+3 on instance]

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有人能给我解释一下如何找到重复项以及计算这些重复项的实例，以便我可以对每个新的重复项实例执行不同的计算吗

我会使用字典来记录使用了哪些值以及使用次数

new_list = [1, 2, 3, 2, 4, 6, 3, 6, 9]

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希望这有帮助

这是一个经过调整的版本，适合粉丝

收藏。defauldict

将集合导入为coll
a_list=[1,2,3,1,2,3,1,2,3]
d=colls.defaultdict（int）
结果=[]
对于列表中的val：
d[val]+=val
结果.追加（d[val]）
打印（结果）

输出：

[1,2,3,2,4,6,3,6,9]

您可以创建一个dict作为计数器，在循环列表时检查每个数字的计数并执行操作。使用集合中的计数器。这里可以找到一个例子。问题是什么？你试过什么，做过什么研究吗？这能回答你的问题吗？我建议你读一下dict方法。它可以用来减少你的压力conditions@Tomerikoo或者

collections.defaultdict

，类似的想法。