Sometimes, while working with Python dictionary lists, one can have a problem in which we require to find the frequency of all the values occurring in a specific key in dictionary list. This can have application across many domains including web development. Let’s discuss certain ways in which this task can be performed.
Input : test_list = [{‘gfg’: [1]}, {‘good’: [5, 78, 10], ‘gfg’: [5, 6, 7, 8]}]
Output : {8: 1, 1: 1, 5: 1, 6: 1, 7: 1}Input : test_list = [{‘gfg’: [1, 5, 6, 7]}]
Output : {1: 1, 5: 1, 6: 1, 7: 1}
Method #1 : Using Counter() + list comprehension
The combination of above functionalities is used to solve this problem. In this, we perform the task of finding frequency using Counter() and computation is done using list comprehension.
# Python3 code to demonstrate working of # Values frequencies of key # Using Counter() + list comprehension from collections import Counter # initializing list test_list = [{'gfg' : [1, 5, 6, 7], 'is' : [9, 6, 2, 10]}, {'gfg' : [5, 6, 7, 8], 'good' : [5, 7, 10]}, {'gfg' : [7, 5], 'best' : [5, 7]}] # printing original list print("The original list is : " + str(test_list)) # frequency key freq_key = "gfg" # Values frequencies of key # Using Counter() + list comprehension res = Counter([idx for val in test_list for idx in val[freq_key]]) # printing result print("The frequency dictionary : " + str(dict(res))) |
The original list is : [{‘gfg’: [1, 5, 6, 7], ‘is’: [9, 6, 2, 10]}, {‘gfg’: [5, 6, 7, 8], ‘good’: [5, 7, 10]}, {‘gfg’: [7, 5], ‘best’: [5, 7]}]
The frequency dictionary : {8: 1, 1: 1, 5: 3, 6: 2, 7: 3}
Method #2 : Using chain.from_iterables() + Counter()
The combination of above methods can be used to solve this problem. In this, we perform the task of iteration and binding using chain.from_iterables().
# Python3 code to demonstrate working of # Values frequencies of key # Using chain.from_iterables() + Counter() from collections import Counter import itertools # initializing list test_list = [{'gfg' : [1, 5, 6, 7], 'is' : [9, 6, 2, 10]}, {'gfg' : [5, 6, 7, 8], 'good' : [5, 7, 10]}, {'gfg' : [7, 5], 'best' : [5, 7]}] # printing original list print("The original list is : " + str(test_list)) # frequency key freq_key = "gfg" # Values frequencies of key # Using chain.from_iterables() + Counter() res = Counter(itertools.chain.from_iterable([sub[freq_key] for sub in test_list])) # printing result print("The frequency dictionary : " + str(dict(res))) |
The original list is : [{‘gfg’: [1, 5, 6, 7], ‘is’: [9, 6, 2, 10]}, {‘gfg’: [5, 6, 7, 8], ‘good’: [5, 7, 10]}, {‘gfg’: [7, 5], ‘best’: [5, 7]}]
The frequency dictionary : {8: 1, 1: 1, 5: 3, 6: 2, 7: 3}
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