Python - 查找特定键的每个值的出现次数

给定一个字典列表，对于一个特定的键，找出该键的每个值出现的次数。

Input : test_list = [{‘gfg’ : 3, ‘best’ : 4}, {‘gfg’ : 3, ‘best’ : 5}, 
{‘gfg’ : 4, ‘best’ : 4}, {‘gfg’ : 7, ‘best’ : 4} ], K = ‘gfg’ 
Output : [{3: 2}, {4: 1}, {7: 1}] 
Explanation : gfg has 2 occurrences of 3 as values.

Input : test_list = [{‘gfg’ : 3, ‘best’ : 4}, {‘gfg’ : 3, ‘best’ : 5}, 
{‘gfg’ : 4, ‘best’ : 4}, {‘gfg’ : 7, ‘best’ : 4} ], K = ‘best’ 
Output : [{4: 3}, {5: 1}] 
Explanation : best has 3 occurrences of 4 as values.

方法 #1：使用groupby() + 字典理解

在这里，我们使用 groupby() 对键的值进行分组，并使用字典理解和 len() 组合和提取值频率。

Python3

# Python3 code to demonstrate working of 
# Values Frequency grouping of K in dictionaries
# Using groupby() + dictionary comprehension
from itertools import groupby
  
# initializing list
test_list = [{'gfg' : 3, 'best' : 4}, {'gfg' : 3, 'best' : 5}, 
             {'gfg' : 4, 'best' : 4}, {'gfg' : 7, 'best' : 4} ]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = 'gfg'
  
# groupby() used to group values and len() to compute Frequency
res = [{key: len(list(val))} for key, val in groupby(test_list, lambda sub: sub[K])]
  
# printing result 
print("The Values Frequency : " + str(res))

输出：

The original list is : [{‘gfg’: 3, ‘best’: 4}, {‘gfg’: 3, ‘best’: 5}, {‘gfg’: 4, ‘best’: 4},
{‘gfg’: 7, ‘best’: 4}]
The Values Frequency : [{3: 2}, {4: 1}, {7: 1}]

方法 #2：使用Counter()

在这里，执行频率检查的任务是使用 Counter() 完成的。在单个字典中返回结果。

蟒蛇3

# Python3 code to demonstrate working of 
# Values Frequency grouping of K in dictionaries
# Using Counter()
from collections import Counter
  
# initializing list
test_list = [{'gfg' : 3, 'best' : 4}, {'gfg' : 3, 'best' : 5}, 
             {'gfg' : 4, 'best' : 4}, {'gfg' : 7, 'best' : 4} ]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K 
K = 'gfg'
  
# groupby() used to group values and len() to compute Frequency
res = dict(Counter(sub[K] for sub in test_list))
  
# printing result 
print("The Values Frequency : " + str(res))

输出：

The original list is : [{‘gfg’: 3, ‘best’: 4}, {‘gfg’: 3, ‘best’: 5}, {‘gfg’: 4, ‘best’: 4},
{‘gfg’: 7, ‘best’: 4}]
The Values Frequency : [{3: 2}, {4: 1}, {7: 1}]