Python | Select dictionary with condition given key greater than k

Last Updated : 27 Apr, 2023

In Python, sometimes we require to get only some of the dictionary required to solve the problem. This problem is quite common in web development that we require to get only the selective dictionary satisfying some given criteria. Let’s discuss certain ways in which this problem can be solved.

Method #1: Using list comprehension

Python3

# Python3 code to demonstrate 
# filtering of a list of dictionary 
# on basis of condition 
 
# initialising list of dictionary 
ini_list = [{'a':1, 'b':3, 'c':7}, {'a':3, 'b':8, 'c':17}, 
            {'a':78, 'b':12, 'c':13}, {'a':2, 'b':2, 'c':2}] 
 
# printing initial list of dictionary 
print ("initial_list", str(ini_list)) 
 
# code to filter list 
# where c is greater than 10 
res = [d for d in ini_list if d['c'] > 10] 
 
# printing result 
print ("resultant_list", str(res)) 

Output

initial_list [{'a': 1, 'b': 3, 'c': 7}, {'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}, {'a': 2, 'b': 2, 'c': 2}]
resultant_list [{'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}]

Time complexity: O(n), where n is the number of key-value pairs in the dictionary.
Auxiliary space: O(n), to store the keys and values in dictionary.

Method #2: Using lambda and filter

Python3

# Python3 code to demonstrate 
# filtering of list of dictionary 
# on basis of condition 
 
# initialising list of dictionary 
ini_list = [{'a':1, 'b':3, 'c':7}, {'a':3, 'b':8, 'c':17}, 
            {'a':78, 'b':12, 'c':13}, {'a':2, 'b':2, 'c':2}] 
 
# printing initial list of dictionary 
print ("initial_list", str(ini_list)) 
 
# code to filter list 
# where c is less than 10 
res = list(filter(lambda x:x["c"] > 10, ini_list )) 
 
# printing result 
print ("resultant_list", str(res)) 

Output

initial_list [{'a': 1, 'b': 3, 'c': 7}, {'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}, {'a': 2, 'b': 2, 'c': 2}]
resultant_list [{'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}]

Method #3: Using dict comprehension and list comprehension

Python3

# Python3 code to demonstrate 
# filtering of list of dictionary 
# on basis of condition 
 
# initialising list of dictionary 
ini_list = [{'a':1, 'b':3, 'c':7}, {'a':3, 'b':8, 'c':17}, 
            {'a':78, 'b':12, 'c':13}, {'a':2, 'b':2, 'c':10}] 
                 
# printing initial list of dictionary 
print ("initial_list", str(ini_list)) 
 
# code to filter list 
# where c is more than 10 
 
res = [{ k:v for (k, v) in i.items()} 
        for i in ini_list if i.get('c') > 10] 
 
# printing result 
print ("resultant_list", str(res)) 

Output

initial_list [{'a': 1, 'b': 3, 'c': 7}, {'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}, {'a': 2, 'b': 2, 'c': 10}]
resultant_list [{'a': 3, 'b': 8, 'c': 17}, {'a': 78, 'b': 12, 'c': 13}]

Time Complexity: The time complexity of this program is O(n), where n is the number of dictionaries in ini_list.

Auxiliary Space: The auxiliary space used by this program is O(n), where n is the number of dictionaries in ini_list.

Using a for loop:

Approach:

Create a new empty dictionary
Iterate over the key-value pairs in the original dictionary using a for loop
If the key is greater than k, add the key-value pair to the new dictionary
Return the new dictionary

Python3

d = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
k = 'c'
new_d = {}
for key, value in d.items():
    if key > k:
        new_d[key] = value
print(new_d)

Output

{'d': 4}

Time complexity: O(n), where n is the number of key-value pairs in the original dictionary
Space complexity: O(n), where n is the number of key-value pairs in the new dictionary

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