使用特定標准的列表中項目的組合

Question

我正在嘗試在列表中查找特定的項目組合。 該列表由重復 y 次的 x 組組成。 在這個例子中，x 和 y = 3，但實際上可能更大。 我想找到組和 y 的每個組合，但不復制給定組合的 x 值。 我認為只展示一個我想要的例子更容易。

這是一個例子。

A = ['ST1_0.245', 'ST1_0.29', 'ST1_0.335', 'ST2_0.245', 'ST2_0.29', 'ST2_0.335', 'ST3_0.245', 'ST3_0.29', 'ST3_0.335']

所以三個組，ST1、ST2 和 ST3——每個都有 3 次迭代，0.245、0.290 和 0.335。

我想找到以下組合。

('ST1_0.245', 'ST2_0.245', 'ST3_0.245')
('ST1_0.245', 'ST2_0.245', 'ST3_0.29')
('ST1_0.245', 'ST2_0.245', 'ST3_0.335')
('ST1_0.245', 'ST2_0.29', 'ST3_0.245')
('ST1_0.245', 'ST2_0.29', 'ST3_0.29')
('ST1_0.245', 'ST2_0.29', 'ST3_0.335')
('ST1_0.245', 'ST2_0.335', 'ST3_0.245')
('ST1_0.245', 'ST2_0.335', 'ST3_0.29')
('ST1_0.245', 'ST2_0.335', 'ST3_0.335')
('ST1_0.29', 'ST2_0.245', 'ST3_0.245')
('ST1_0.29', 'ST2_0.245', 'ST3_0.29')
('ST1_0.29', 'ST2_0.245', 'ST3_0.335')
('ST1_0.29', 'ST2_0.29', 'ST3_0.245')
('ST1_0.29', 'ST2_0.29', 'ST3_0.29')
('ST1_0.29', 'ST2_0.29', 'ST3_0.335')
('ST1_0.29', 'ST2_0.335', 'ST3_0.245')
('ST1_0.29', 'ST2_0.335', 'ST3_0.29')
('ST1_0.29', 'ST2_0.335', 'ST3_0.335')
('ST1_0.335', 'ST2_0.245', 'ST3_0.245')
('ST1_0.335', 'ST2_0.245', 'ST3_0.29')
('ST1_0.335', 'ST2_0.245', 'ST3_0.335')
('ST1_0.335', 'ST2_0.29', 'ST3_0.245')
('ST1_0.335', 'ST2_0.29', 'ST3_0.29')
('ST1_0.335', 'ST2_0.29', 'ST3_0.335')
('ST1_0.335', 'ST2_0.335', 'ST3_0.245')
('ST1_0.335', 'ST2_0.335', 'ST3_0.29')
('ST1_0.335', 'ST2_0.335', 'ST3_0.335')

請注意，ST1、ST2 和 ST3 僅在每個組合中出現一次。

這是我至少在小案例中工作的代碼。

import itertools
import numpy as np

comb = []
gr_list=['ST1','ST2','ST3']
for itr in itertools.combinations(A, len(gr_list)):
    # pdb.set_trace()
    for n in np.arange(len(gr_list)):
        if sum(itr[n].split('_')[0] in s for s in itr) > 1:
            break
    
    if n == len(gr_list)-1:
        comb.append(itr)

這適用於我測試的幾個小例子，但是當我嘗試更大的值時，我得到的結果比我想象的要多，但這可能是我嘗試計算預期數量時的錯誤。 但無論哪種方式，都需要太長時間。 有沒有更快的方法來做到這一點？

我確實分別擁有這兩個值。 在我寫這篇文章時，我覺得這是一種更好的方法來處理它，但我也不知道該怎么做。

Answer 1

您可以為此使用itertools.product ，它將生成一個迭代器而不是一個列表（如果您是迭代而不是生成整個集合，這通常會更有效）。 您最終將得到不同類別長度的乘積作為迭代器中元素的數量。

Answer 2

根據需要創建組，然后在組上使用itertools.product ：

A = ['ST1_0.245', 'ST1_0.29', 'ST1_0.335', 
     'ST2_0.245', 'ST2_0.29', 'ST2_0.335', 
     'ST3_0.245', 'ST3_0.29', 'ST3_0.335']

prefixes = set(s.split("_")[0] for s in A)
groups = [[a for a in A if a.split("_")[0]==p] for p in prefixes]

>>> list(itertools.product(*groups))

[('ST2_0.245', 'ST3_0.245', 'ST1_0.245'),
 ('ST2_0.245', 'ST3_0.245', 'ST1_0.29'),
 ('ST2_0.245', 'ST3_0.245', 'ST1_0.335'),
 ('ST2_0.245', 'ST3_0.29', 'ST1_0.245'),
 ('ST2_0.245', 'ST3_0.29', 'ST1_0.29'),
 ('ST2_0.245', 'ST3_0.29', 'ST1_0.335'),
 ('ST2_0.245', 'ST3_0.335', 'ST1_0.245'),
 ('ST2_0.245', 'ST3_0.335', 'ST1_0.29'),
 ('ST2_0.245', 'ST3_0.335', 'ST1_0.335'),
 ('ST2_0.29', 'ST3_0.245', 'ST1_0.245'),
 ('ST2_0.29', 'ST3_0.245', 'ST1_0.29'),
 ('ST2_0.29', 'ST3_0.245', 'ST1_0.335'),
 ('ST2_0.29', 'ST3_0.29', 'ST1_0.245'),
 ('ST2_0.29', 'ST3_0.29', 'ST1_0.29'),
 ('ST2_0.29', 'ST3_0.29', 'ST1_0.335'),
 ('ST2_0.29', 'ST3_0.335', 'ST1_0.245'),
 ('ST2_0.29', 'ST3_0.335', 'ST1_0.29'),
 ('ST2_0.29', 'ST3_0.335', 'ST1_0.335'),
 ('ST2_0.335', 'ST3_0.245', 'ST1_0.245'),
 ('ST2_0.335', 'ST3_0.245', 'ST1_0.29'),
 ('ST2_0.335', 'ST3_0.245', 'ST1_0.335'),
 ('ST2_0.335', 'ST3_0.29', 'ST1_0.245'),
 ('ST2_0.335', 'ST3_0.29', 'ST1_0.29'),
 ('ST2_0.335', 'ST3_0.29', 'ST1_0.335'),
 ('ST2_0.335', 'ST3_0.335', 'ST1_0.245'),
 ('ST2_0.335', 'ST3_0.335', 'ST1_0.29'),
 ('ST2_0.335', 'ST3_0.335', 'ST1_0.335')]