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Python – Frequency Grouping Dictionary
  • Last Updated : 04 May, 2020

Sometimes, while working with Python dictionaries, we can have a problem in which we need to perform the grouping of dictionary data, in a way in which we need to group all the similar dictionaries key with its frequency. This kind of problem has its application in web development domain. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [{‘best’: 2, ‘Gfg’: 1}, {‘best’: 2, ‘Gfg’: 1}]
Output : [{‘freq’: 2, ‘Gfg’: 1}]

Input : test_list = [{‘Gfg’: 1, ‘best’: 2}, {‘Gfg’: 2, ‘best’: 1}]
Output : [{‘Gfg’: 1, ‘freq’: 1}, {‘Gfg’: 2, ‘freq’: 1}]

Method #1 : Using defaultdict() + list comprehension
The combination of above functions can be used to perform this task. In this, we initialize the defaultdict with integer to get the frequency and list comprehension is used to compile the resultant dictionary.




# Python3 code to demonstrate working of 
# Frequency Grouping Dictionary
# Using defaultdict() + list comprehension
from collections import defaultdict
  
# initializing list
test_list = [{'Gfg' 1, 'best' : 2}, 
             {'Gfg' 1, 'best' : 2},
             {'Gfg' 2, 'good' : 3},
             {'Gfg' 2, 'best' : 2},
             {'Gfg' 2, 'good' : 3}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Frequency Grouping Dictionary
# Using defaultdict() + list comprehension
temp = defaultdict(int)
for sub in test_list:
    key = sub['Gfg']
    temp[key] += 1
  
res = [{"Gfg": key, "freq": val} for (key, val) in temp.items()]
  
# printing result 
print("The frequency dictionary : " + str(res)) 
Output :



The original list is : [{‘Gfg’: 1, ‘best’: 2}, {‘Gfg’: 1, ‘best’: 2}, {‘good’: 3, ‘Gfg’: 2}, {‘Gfg’: 2, ‘best’: 2}, {‘good’: 3, ‘Gfg’: 2}]
The frequency dictionary : [{‘Gfg’: 1, ‘freq’: 2}, {‘Gfg’: 2, ‘freq’: 3}]

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