如何找到最大值？

Question

我需要找到例如值的最大值：

[(12, 0.95), (15, 0.92), (20, 0.90), (12, 0.88), (15, 0.98), (12, 0.89)] 

輸出最大值與ID對應：

[(12, 0.95), (15, 0.98), (20, 0.90)] 

我怎樣才能在Python實現這一目標？

任何建議！感謝您的幫助

Answer 1

只需使用基礎知識：

data = [(12, 0.95), (15, 0.92), (20, 0.90), (12, 0.88), (15, 0.98), (12, 0.89)] 

result_dict = {} 
for id_num, value in data: 
    result_dict[id_num] = max(value, result_dict.get(id_num, value)) 

result = sorted(result_dict.items()) 

print(result) 

如果環路內的部分是混亂的，這裏有其他的方式來寫它：

if id_num in result_dict: 
    result_dict[id_num] = max(result_dict[id_num], value) 
else: 
    result_dict[id_num] = value 

或

if id_num in result_dict: 
    if value > result_dict[id_num]: 
     result_dict[id_num] = value 
else: 
    result_dict[id_num] = value 

或

if id_num not in result_dict or value > result_dict[id_num]: 
    result_dict[id_num] = value 

或

if id_num > result_dict.get(id_num, value): 
    result_dict[id_num] = value 

Answer 2

排序，groupby和max！

import itertools 
import operator 

data = [(12, 0.95), (15, 0.92), (20, 0.90), (12, 0.88), (15, 0.98), (12, 0.89)] 
sorted_data = sorted(data) 
groups = itertools.groupby(sorted_data, key=operator.itemgetter(0)) 
result = [max(group) for _, group in groups] 

itertools.groupby採取項目的排序列表，通過一些關鍵功能組他們（在這種情況下，我們使用operator.itemgetter(0)），併爲您提供以下形式的迭代器：

[(keyfunc_result, [list_of_results...], ... ]