如何将列表中字符串的位置添加到新的双打列表中？

Question

示例：

r 是加载到列表中的文本文件

r = ['John is american', 'Bea is french', 'John is american', 'Ray is german', 'John is american', 'Bea is french', 'Bea is french', '', 'Lisa is dutch']

我想做的是统计出现的次数，并在r中添加位置：

finallist = ['string', frequency, [positions in r]]

finallist = [['John is american', 3, [0,2,4]], ['Bea is french', 3, [1,5,6]], ['Ray is german', 1, [3]], ['Lisa is dutch', 1, [7]]]

我知道如何计算 r:

中的字符串

[[x,r.count(x)] for x in set(r)]

（或使用 collections 库中的计数器 class）

但是如何将字符串在 r 中的位置添加到决赛列表中？

Answer 1

使用字典来跟踪句子的位置（构建列表）；这些列表的最终长度也是频率计数：

from collections import defaultdict

pos = defaultdict(list)
for i, sentence in enumerate(r):
    pos[sentence].append(i)
finallist = [[sentence, len(positions), positions] for sentence, positions in pos.items()]

演示：

>>> from collections import defaultdict
>>> r = ['John is american', 'Bea is french', 'John is american', 'Ray is german', 'John is american', 'Bea is french', 'Bea is french', '', 'Lisa is dutch']
>>> pos = defaultdict(list)
>>> for i, sentence in enumerate(r):
...     pos[sentence].append(i)
...
>>> [[sentence, len(positions), positions] for sentence, positions in pos.items()]
[['John is american', 3, [0, 2, 4]], ['Bea is french', 3, [1, 5, 6]], ['Ray is german', 1, [3]], ['', 1, [7]], ['Lisa is dutch', 1, [8]]]

如果输出顺序很重要，并且您还没有访问 Python 3.6（在回答这个问题时是 in beta，但其 dict 实现保留了插入顺序)，那么你可以使用一个 OrderedDict 实例，并使用 dict.setdefault() 来具体化每个键的初始空列表：

from collections import OrderedDict

pos = OrderedDict()
for i, sentence in enumerate(r):
    pos.setdefault(sentence, []).append(i)
finallist = [[sentence, len(positions), positions] for sentence, positions in pos.items()]

如何将列表中字符串的位置添加到新的双打列表中？

How to add position of a string in a list to a new list of doubles?

python

position

list

count

python-3.x