Python – Maximum record value key in dictionary

Sometimes, while working with dictionary records, we can have problem in which we need to find the key with maximum value of particular key of nested records in list. This can have application in domains such as web development and Machine Learning. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop
This is brute force way in which this task can be performed. In this, we iterate through each key for keys and assign to max, the maximum of required key in nested record.

# Python3 code to demonstrate working of
# Maximum record value key in dictionary
# Using loop

# initializing dictionary
test_dict = {'gfg' : {'Manjeet' : 5, 'Himani' : 10},
             'is' : {'Manjeet' : 8, 'Himani' : 9},
             'best' : {'Manjeet' : 10, 'Himani' : 15}}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# initializing search key
key = 'Himani'

# Maximum record value key in dictionary
# Using loop
res = None
res_max = 0
for sub in test_dict:
    if test_dict[sub][key] > res_max:
        res_max = test_dict[sub][key]
        res = sub

# printing result
print("The required key is : " + str(res))

Output :

The original dictionary is : {‘best’: {‘Himani’: 15, ‘Manjeet’: 10}, ‘gfg’: {‘Himani’: 10, ‘Manjeet’: 5}, ‘is’: {‘Himani’: 9, ‘Manjeet’: 8}}
The required key is : best

Method #2 : Using max() + lambda function
This is one liner approach to solve this problem. In this, we perform the task of iteration using max key argument, passing a lambda function which binds the required logic.

# Python3 code to demonstrate working of
# Maximum record value key in dictionary
# Using max() + lambda function

# initializing dictionary
test_dict = {'gfg' : {'Manjeet' : 5, 'Himani' : 10},
             'is' : {'Manjeet' : 8, 'Himani' : 9},
             'best' : {'Manjeet' : 10, 'Himani' : 15}}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# initializing search key
key = 'Himani'

# Maximum record value key in dictionary
# Using max() + lambda function
res = max(test_dict, key = lambda sub: test_dict[sub][key])

# printing result
print("The required key is : " + str(res))

Output :

The original dictionary is : {‘best’: {‘Himani’: 15, ‘Manjeet’: 10}, ‘gfg’: {‘Himani’: 10, ‘Manjeet’: 5}, ‘is’: {‘Himani’: 9, ‘Manjeet’: 8}}
The required key is : best