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Python | Count keys with particular value in dictionary

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  • Difficulty Level : Hard
  • Last Updated : 22 Jun, 2022
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Sometimes, while working with Python dictionaries, we can come across a problem in which we have a particular value, and we need to find frequency if it’s occurrence. Let’s discuss certain ways in which this problem can be solved. Method #1 : Using loop This problem can be solved using naive method of loop. In this we just iterate through each key in dictionary and when a match is found, the counter is increased. 

Python3




# Python3 code to demonstrate working of
# Count keys with particular value in dictionary
# Using loop
 
# Initialize dictionary
test_dict = {'gfg' : 1, 'is' : 2, 'best' : 3, 'for' : 2, 'CS' : 2}
 
# printing original dictionary
print("The original dictionary : " +  str(test_dict))
 
# Initialize value
K = 2
 
# Using loop
# Selective key values in dictionary
res = 0
for key in test_dict:
    if test_dict[key] == K:
        res = res + 1
     
# printing result
print("Frequency of K is : " + str(res))


Output

The original dictionary : {'gfg': 1, 'is': 2, 'best': 3, 'for': 2, 'CS': 2}
Frequency of K is : 3

  Method #2 : Using sum() + values() This can also be solved using the combination of sum() and value(). In this, sum is used to perform the summation of values filtered and values of dictionary are extracted using values() 

Python3




# Python3 code to demonstrate working of
# Count keys with particular value in dictionary
# Using sum() + values()
 
# Initialize dictionary
test_dict = {'gfg' : 1, 'is' : 2, 'best' : 3, 'for' : 2, 'CS' : 2}
 
# printing original dictionary
print("The original dictionary : " +  str(test_dict))
 
# Initialize value
K = 2
 
# Using sum() + values()
# Selective key values in dictionary
res = sum(x == K for x in test_dict.values())
     
# printing result
print("Frequency of K is : " + str(res))


Output

The original dictionary : {'gfg': 1, 'is': 2, 'best': 3, 'for': 2, 'CS': 2}
Frequency of K is : 3

Method #3 : Using count() and values().These methods can be used together to find number of keys with particular value.

Python3




# Python3 code to demonstrate working of
# Count keys with particular value in dictionary
# Using count() + values()
 
# Initialize dictionary
test_dict = {'gfg' : 1, 'is' : 2, 'best' : 3, 'for' : 2, 'CS' : 2}
 
# printing original dictionary
print("The original dictionary : " +  str(test_dict))
 
# Initialize value
K = 2
 
# Using count() + values()
list1=list(test_dict.values())
 
# Selective key values in dictionary
res = list1.count(K)
    
# printing result
print("Frequency of K is : " + str(res))


Output

The original dictionary : {'gfg': 1, 'is': 2, 'best': 3, 'for': 2, 'CS': 2}
Frequency of K is : 3

Complexity Analysis:

In all the solutions time and space complexity are the same:

Time Complexity: O(n)

Space Complexity: O(n)


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