Python | Extract specific keys from dictionary

We have a lot of variations and applications of dictionary containers in Python and sometimes, we wish to perform a filter of keys in a dictionary, i.e extracting just the keys which are present in the particular container. Let’s discuss certain ways in which this can be performed. 

Extract specific keys from dictionary using dictionary comprehension + items()

This problem can be performed by reconstruction using the keys extracted through the items function that wishes to be filtered and the dictionary function makes the desired dictionary.

Output : 

The original dictionary : {'manjeet': 4, 'akshat': 3, 'akash': 2, 'nikhil': 1}
The filtered dictionary is : {'akshat': 3, 'nikhil': 1}

The time complexity of the given code is O(n), where n is the number of elements in the dictionary. 

The space complexity of the given code is O(k), where k is the number of keys extracted from the dictionary.

Extract specific keys from the dictionary using dict() 

The dict() function can be used to perform this task by converting the logic performed using list comprehension into a dictionary. 

Output : 

The original dictionary : {'manjeet': 4, 'akshat': 3, 'akash': 2, 'nikhil': 1}
The filtered dictionary is : {'akshat': 3, 'nikhil': 1}

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.

Extract specific keys from dictionary using filter()

This method involves using the filter() function to filter the keys in the dictionary:

The original dictionary : {'nikhil': 1, 'akash': 2, 'akshat': 3, 'manjeet': 4}
The filtered dictionary is : {'nikhil': 1, 'akshat': 3}

Time complexity: O(n)
Auxiliary Space: O(n) for storing the result

Extract specific keys from dictionary Using a for loop and a conditional statement 

Initialize the dictionary:

1. Define the list of keys to be extracted.
2. Initialize an empty dictionary to store the extracted keys and their values.
3. Use a for loop and a conditional statement to check if each key in the dictionary is in the list of keys to be extracted. If it is, add the key-value pair to the extracted dictionary.
4. Print the extracted dictionary.

The original dictionary is: {'nikhil': 1, 'akash': 2, 'akshat': 3, 'manjeet': 4}
The extracted dictionary is: {'nikhil': 1, 'akshat': 3}

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 to be extracted

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Article Tags :

• Python
• Python Programs
• Python dictionary-programs

Practice Tags :

• python