Python | Element Occurrence in dictionary of list values

Last Updated : 29 Mar, 2019

Sometimes we can have a task in which we are required to count the occurrences of test elements in list or winning numbers, against the numbers with the associated keys with list as values. This can have applications in gaming or other utilities. Let’s discuss certain ways in which this can be done.

Method #1 : Using dictionary comprehension + sum()
This task can be performed using the combination of above two utilities in which we use dictionary comprehension to bind the logic and sum function can be used to perform the summation of the matches found from test list.

# Python3 code to demonstrate
# Element Occurrence in dictionary value list
# using list comprehension + sum()
  
# initializing dictionary
test_dict = { "Akshat" : [1, 4, 5, 3],
              "Nikhil" : [4, 6],
              "Akash" : [5, 2, 1] }
  
# initializing test list 
test_list = [2, 1]
  
# printing original dict
print("The original dictionary : " + str(test_dict))
  
# printing original list 
print("The original list : " + str(test_list))
  
# using list comprehension + sum()
# Element Occurrence in dictionary value list
res = {idx : sum(1 for i in j if i in test_list)
                for idx, j in test_dict.items()}
  
# print result
print("The summation of element occurrence : " + str(res))

Output :

The original dictionary : {'Nikhil': [4, 6], 'Akshat': [1, 4, 5, 3], 'Akash': [5, 2, 1]}
The original list : [2, 1]
The summation of element occurrence : {'Nikhil': 0, 'Akshat': 1, 'Akash': 2}

Method #2 : Using collections.Counter()
Python offers an inbuilt function that performs the task of extracting the frequency and using this and conditioning to presence in test list, we can solve the above problem using this function.

# Python3 code to demonstrate
# Element Occurrence in dictionary value list
# using collections.Counter()
from collections import Counter
  
# initializing dictionary
test_dict = { "Akshat" : [1, 4, 5, 3],
              "Nikhil" : [4, 6],
              "Akash" : [5, 2, 1] }
  
# initializing test list 
test_list = [2, 1]
  
# printing original dict
print("The original dictionary : " + str(test_dict))
  
# printing original list 
print("The original list : " + str(test_list))
  
# using collections.Counter()
# Element Occurrence in dictionary value list
# omits the 0 occurrence word key
res = dict(Counter(j for j in test_dict
           for i in test_list if i in test_dict[j]))
  
# print result
print("The summation of element occurrence : " + str(res))

Output :

The original dictionary : {'Nikhil': [4, 6], 'Akshat': [1, 4, 5, 3], 'Akash': [5, 2, 1]}
The original list : [2, 1]
The summation of element occurrence : {'Akshat': 1, 'Akash': 2}

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