Python – Keys with shortest length lists in dictionary

Last Updated : 13 Apr, 2023

Sometimes, while working with Python lists, we can have problem in which we need to return the keys which have minimum lengths of lists as values. This can have application in domains in which we work with data. Lets discuss certain ways in which this task can be performed.

Method #1: Using len() + loop + items()

The combination of above functions can be used to perform this task. In this, we iterate the keys of dictionary and return all the keys whose lengths equates the length of smallest list using len().

Python3

# Python3 code to demonstrate working of 
# Keys with shortest length lists in dictionary
# Using len() + loop + items()
 
# initializing dictionary
test_dict = {'gfg' : [4, 5],
             'is' : [9, 7, 3, 10],
             'best' : [11, 34],
             'for' : [6, 8, 2], 
             'geeks' : [12, 24]}
 
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
 
# Keys with shortest length lists in dictionary
# Using len() + loop + items()
min_val = min([len(test_dict[ele]) for ele in test_dict])
res = []
for ele in test_dict:
    if len(test_dict[ele]) == min_val:
        res.append(ele)
         
# printing result 
print("The required keys are : " + str(res)) 

Output :

The original dictionary is : {‘is’: [9, 7, 3, 10], ‘gfg’: [4, 5], ‘best’: [11, 34], ‘for’: [6, 8, 2], ‘geeks’: [12, 24]} The required keys are : [‘gfg’, ‘best’, ‘geeks’]

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #2: Using list comprehension

This task can also be performed using a shorthand of list comprehension. In this, we perform the task similar to above task but in shorthand manner.

Python3

# Python3 code to demonstrate working of 
# Keys with shortest length lists in dictionary
# Using list comprehension
 
# initializing dictionary
test_dict = {'gfg' : [4, 5],
             'is' : [9, 7, 3, 10],
             'best' : [11, 34],
             'for' : [6, 8, 2], 
             'geeks' : [12, 24]}
 
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
 
# Keys with shortest length lists in dictionary
# Using list comprehension
min_val = min([len(test_dict[ele]) for ele in test_dict])
res = [key for key, val in test_dict.items() if len(val) == min_val] 
         
# printing result 
print("The required keys are : " + str(res)) 

Output :

The original dictionary is : {‘is’: [9, 7, 3, 10], ‘gfg’: [4, 5], ‘best’: [11, 34], ‘for’: [6, 8, 2], ‘geeks’: [12, 24]} The required keys are : [‘gfg’, ‘best’, ‘geeks’]

The time complexity of this program is O(n), where n is the number of key-value pairs in the test_dict dictionary.

The auxiliary space complexity of this program is O(m), where m is the number of keys in the test_dict dictionary.

Method 3: Using dictionary comprehension.

Step-by-step approach:

Initialize a variable min_length with the length of the shortest list value in the dictionary.
Use dictionary comprehension to create a new dictionary with only the key-value pairs where the value list has length equal to min_length.
Extract the keys from the new dictionary as a list.

Below is the implementation of the above approach:

Python3

# Python3 code to demonstrate working of 
# Keys with shortest length lists in dictionary
# Using dictionary comprehension
 
# initializing dictionary
test_dict = {'gfg' : [4, 5],
             'is' : [9, 7, 3, 10],
             'best' : [11, 34],
             'for' : [6, 8, 2], 
             'geeks' : [12, 24]}
 
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
 
# Keys with shortest length lists in dictionary
# Using dictionary comprehension
min_length = min(len(lst) for lst in test_dict.values())
res = {k: v for k, v in test_dict.items() if len(v) == min_length}
keys = list(res.keys())
 
# printing result
print("The required keys are : " + str(keys))

Output

The original dictionary is : {'gfg': [4, 5], 'is': [9, 7, 3, 10], 'best': [11, 34], 'for': [6, 8, 2], 'geeks': [12, 24]}
The required keys are : ['gfg', 'best', 'geeks']

Time complexity: O(n), where n is the number of key-value pairs in the dictionary.
Auxiliary space: O(k), where k is the number of keys in the new dictionary created by dictionary comprehension.

Python | Initializing dictionary with list index-values

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Python – Keys with shortest length lists in dictionary

Method #1: Using len() + loop + items()

Python3

Method #2: Using list comprehension

Python3

Method 3: Using dictionary comprehension.

Python3

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