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Python – Values frequency across Dictionaries lists
  • Last Updated : 01 Aug, 2020

Given two list of dictionaries, compute frequency corresponding to each value in dictionary 1 to second.

Input : test_list1 = [{“Gfg” : 6}, {“best” : 10}], test_list2 = [{“a” : 6}, {“b” : 10}, {“d” : 6}}]
Output : {‘Gfg’: 2, ‘best’: 1}
Explanation : 6 has 2 occurrence in 2nd list, 10 has 1.

Input : test_list1 = [{“Gfg” : 6}], test_list2 = [{“a” : 6}, {“b” : 6}, {“d” : 6}}]
Output : {‘Gfg’: 3}
Explanation : 6 has 3 occurrence in 2nd list.

Method : Using dictionary comprehension + count() + list comprehension

 The combination of above functionalities can be used to solve this problem. In this, we perform this task using 2 steps, in first we extract all values from second list, and then perform mapping with frequency with first dictionary using list comprehension and count().



Python3




# Python3 code to demonstrate working of 
# Values frequency across Dictionaries lists
# Using list comprehension + dictionary comprehension + count()
  
# initializing lists
test_list1 = [{"Gfg" : 6}, {"is" : 9}, {"best" : 10}]
test_list2 = [{"a" : 6}, {"b" : 10}, {"c" : 9}, {"d" : 6}, {"e" : 9}, {"f" : 9}]
  
# printing original list
print("The original list 1 : " + str(test_list1))
print("The original list 2 : " + str(test_list2))
  
# extracting values from target dictionary
temp = [val for sub in test_list2 for key, val in sub.items()]
  
# frequency mapping from 1st dictionary keys 
res = {key : temp.count(val) for sub in test_list1 for key, val in sub.items()}
  
# printing result 
print("The frequency dictionary : " + str(res))
Output
The original list 1 : [{'Gfg': 6}, {'is': 9}, {'best': 10}]
The original list 2 : [{'a': 6}, {'b': 10}, {'c': 9}, {'d': 6}, {'e': 9}, {'f': 9}]
The frequency dictionary : {'Gfg': 2, 'is': 3, 'best': 1}

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