如何将计数数字附加到Python中列表中的重复项? [英] How to append count numbers to duplicates in a list in Python?

问题描述

以下是包含重复项的列表:

Here is a list containing duplicates:

l1 = ['a', 'b', 'c', 'a', 'a', 'b']

这是预期的结果:

l1 = ['a', 'b', 'c', 'a_1', 'a_2', 'b_1']

如何通过添加计数来重命名重复项?

How can the duplicates be renamed by appending a count number?

这里是实现这一目标的尝试；但是，还有一种更Python化的方法吗?

Here is an attempt to achieve this goal; however, is there a more Pythonic way?

for index in range(len(l1)):
    counter = 1
    list_of_duplicates_for_item = [dup_index for dup_index, item in enumerate(l1) if item == l1[index] and l1.count(l1[index]) > 1]
    for dup_index in list_of_duplicates_for_item[1:]: 
        l1[dup_index] = l1[dup_index] + '_' + str(counter)
        counter = counter + 1

推荐答案

在Python中，生成新列表通常比更改现有列表容易得多.我们有发电机可以有效地做到这一点.字典可以保留发生次数.

In Python, generating a new list is usually much easier than changing an existing list. We have generators to do this efficiently. A dict can keep count of occurrences.

l = ['a', 'b', 'c', 'a', 'a', 'b']

def rename_duplicates( old ):
    seen = {}
    for x in old:
        if x in seen:
            seen[x] += 1
            yield "%s_%d" % (x, seen[x])
        else:
            seen[x] = 0
            yield x

print list(rename_duplicates(l))

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