提取N个最大字典键的Python程序

给定一个字典，按降序提取最大的 N 个字典键。

Input : test_dict = {6 : 2, 8: 9, 3: 9, 10: 8}, N = 3 
Output : [10, 8, 6] 
Explanation : Max. N keys extracted in descending order.

Input : test_dict = {6 : 2, 8: 9, 3: 9, 10: 8}, N = 2 
Output : [10, 8] 
Explanation : Max. N keys extracted in descending order. 

方法 #1：使用 sorted() + lambda + reverse

以上功能的组合可以解决这个问题。在此，我们使用 sorted() + lambda 执行按键排序，而 reverse 用于执行反向排序以获得所需的排序。

Python3

# Python3 code to demonstrate working of 
# Extract top N Dictionaries by Key
# Using sorted() + lambda + reverse
  
# initializing dictionary
test_dict = {6 : 2, 8: 9, 3: 9, 10: 8}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing N 
N = 4
  
res = []
  
# 0 in lambda used for keys, list sliced till N for top N values
for key, val in sorted(test_dict.items(), key = lambda x: x[0], reverse = True)[:N]:
    res.append(key)
  
# printing result 
print("Top N keys are: " + str(res))

输出

The original dictionary is : {6: 1, 8: 9, 3: 9, 10: 8}
Top N keys are: [10, 8, 6, 3]

方法 #2：使用 nlargest() + lambda

这是可以执行此任务的另一种方式。其中，使用 nlargest() 提取最大值，并使用 lambda函数来驱动键提取和比较逻辑。

蟒蛇3

# Python3 code to demonstrate working of 
# Extract top N Dictionaries by Key
# Using nlargest() + lambda
from heapq import nlargest
  
# initializing dictionary
test_dict = {6 : 2, 8: 9, 3: 9, 6: 1, 10: 8}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing N 
N = 4
  
res = []
  
# Using nlargest() to get maximum keys 
for key, val in nlargest(N, test_dict.items(), key = lambda ele: ele[0]):
    res.append(key)
      
# printing result 
print("Top N keys are: " + str(res))

输出

The original dictionary is : {6: 1, 8: 9, 3: 9, 10: 8}
Top N keys are: [10, 8, 6, 3]