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Python | N largest values in dictionary

  • Last Updated : 26 Aug, 2019
Geek Week

Many times while working with Python dictionary, we can have a particular problem to find the N maxima of values in numerous keys. This problem is quite common while working with web development domain. Let’s discuss several ways in which this task can be performed.

Method #1 : itemgetter() + items() + sorted()

The combination of above method is used to perform this particular task. In this, we just reverse sort the dictionary values expressed using itemgetter() and accessed using items().




# Python3 code to demonstrate working of
# N largest values in dictionary
# Using sorted() + itemgetter() + items()
from operator import itemgetter
  
# Initialize dictionary
test_dict = {'gfg' : 1, 'is' : 4, 'best' : 6, 'for' : 7, 'geeks' : 3 }
  
# Initialize N 
N = 3
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# N largest values in dictionary
# Using sorted() + itemgetter() + items()
res = dict(sorted(test_dict.items(), key = itemgetter(1), reverse = True)[:N])
  
# printing result
print("The top N value pairs are  " + str(res))
Output :
The original dictionary is : {'best': 6, 'gfg': 1, 'geeks': 3, 'for': 7, 'is': 4}
The top N value pairs are  {'for': 7, 'is': 4, 'best': 6}

 



Method #2 : Using nlargest()
This task can be performed using the nlargest function. This is inbuilt function in heapq library which internally performs this task and can be used to do it externally. Has the drawback of printing just keys not values.




# Python3 code to demonstrate working of
# N largest values in dictionary
# Using nlargest
from heapq import nlargest
  
# Initialize dictionary
test_dict = {'gfg' : 1, 'is' : 4, 'best' : 6, 'for' : 7, 'geeks' : 3 }
  
# Initialize N 
N = 3
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# N largest values in dictionary
# Using nlargest
res = nlargest(N, test_dict, key = test_dict.get)
  
# printing result
print("The top N value pairs are  " + str(res))
Output :
The original dictionary is : {'gfg': 1, 'best': 6, 'geeks': 3, 'for': 7, 'is': 4}
The top N value pairs are  ['for', 'best', 'is']

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