如何用元组中的一个项筛选元组列表?

sorted_res = sorted(d, key = lambda x:((x[0], x[1]), x[2]),reverse=True)
print(sorted_res)

[('C', 'D', 1),
 ('B', 'D', 2),
 ('B', 'C', 8),
 ('B', 'C', 4),
 ('A', 'D', 3),
 ('A', 'C', 5),
 ('A', 'B', 3),
 ('A', 'B', 1)]

dictionary 前两个元素的键和值将是最新的小元素:

my_dict = {(i[0], i[1]):i for i in sorted_res}
print(my_dict)

{('A', 'B'): ('A', 'B', 1),
 ('A', 'C'): ('A', 'C', 5),
 ('A', 'D'): ('A', 'D', 3),
 ('B', 'C'): ('B', 'C', 4),
 ('B', 'D'): ('B', 'D', 2),
 ('C', 'D'): ('C', 'D', 1)}

list(my_dict.values())

结果:

[('A', 'C', 5),
 ('A', 'B', 1),
 ('A', 'D', 3),
 ('B', 'D', 2),
 ('C', 'D', 1),
 ('B', 'C', 4)]

sorted 和 dictionary comprehension

result = list({(i[0], i[1]):i 
             for i in sorted(d, key = lambda x:((x[0], x[1]), x[2]),reverse=True)}.values())

只是一点重构。

edge_dict = {}

for t in d:
    key = t[:2]
    value = t[-1]
    if key in edge_dict:
        edge_dict[key] = min(value, edge_dict[key]) 
    else:
        edge_dict[key] = value

final_list = [(q,r,t) for (q,r),t in edge_dict.items()]
final_list.sort(key=lambda x: x[2])

itertools.groupby ,并在每个分组中选择最小值:

import itertools
d = [('A', 'B', 1), ('C', 'D', 1), 
 ('B', 'D', 2), ('A', 'B', 3), 
 ('A', 'D', 3), ('B', 'C', 4), 
 ('A', 'C', 5), ('B', 'C', 8)]
new_d = [min(list(b), key=lambda x:x[-1]) for _, b in itertools.groupby(sorted(d, key=lambda x:x[:-1]), key=lambda x:x[:-1])]

[('A', 'B', 1), ('A', 'C', 5), ('A', 'D', 3), ('B', 'C', 4), ('B', 'D', 2), ('C', 'D', 1)]

3. 使用节点对的排序形式作为字典 key

check_dict={} #This will store the minimum valued nodes

for i in d:
    if check_dict.get((i[0],i[1])) ==None: #if the node is absent then add it to the check_dict
        check_dict[tuple(sorted((i[0],i[1])))] = i[2]
    else: #if the node is present then compare with the previous value and store the minimum one
        check_dict[tuple(sorted((i[0],i[1])))] = min(check_dict[(i[0],i[1])],i[2]) #used sorted to treat ('A','B') as same as ('B',A')
expected_list = [tuple(key+(value,)) for key,value in check_dict.items()] #create your list of tuples
print(expected_list)

[('A', 'B', 1), ('C', 'D', 1), ('B', 'D', 2), ('A', 'D', 3), ('B', 'C', 4), ('A', 'C', 5)]