Sometimes, while working with dictionaries, we can have a use-case in which we require to multiply a particular key’s value by K in dictionary. It may seem a quite straight forward problem, but catch comes when the existence of a key is not known, hence becomes a 2 step process at times. Let’s discuss certain ways in which this task can be performed. Method #1 : Using get() The get function can be used to initialize a non-existing key with 1 and then the product is possible. By this way the problem of non-existing key can be avoided.
Python3
# Python3 code to demonstrate working of# Multiply Dictionary Value by Constant# Using get()# Initialize dictionarytest_dict = {'gfg' : 1, 'is' : 2, 'for' : 4, 'CS' : 5}# printing original dictionaryprint("The original dictionary : " + str(test_dict))# Initialize K K = 5# Using get()# Multiply Dictionary Value by Constanttest_dict['best'] = test_dict.get('best', 1) * K # printing result print("Dictionary after the multiplication of key : " + str(test_dict)) |
The original dictionary : {'for': 4, 'is': 2, 'CS': 5, 'gfg': 1}
Dictionary after the multiplication of key : {'for': 4, 'is': 2, 'CS': 5, 'best': 5, 'gfg': 1}
Method #2 : Using defaultdict() This problem can also be solved by using a defaultdict method, which initializes the potential keys and doesn’t throw an exception in case of non-existence of keys.
Python3
# Python3 code to demonstrate working of# Multiply Dictionary Value by Constant# Using defaultdict()from collections import defaultdict# Initialize dictionarytest_dict = defaultdict(int)# printing original dictionaryprint("The original dictionary : " + str(dict(test_dict)))# Initialize K K = 5# Using defaultdict()# Multiply Dictionary Value by Constanttest_dict['best'] *= K # printing result print("Dictionary after the multiplication of key : " + str(dict(test_dict))) |
The original dictionary : {}
Dictionary after the multiplication of key : {'best': 0}
Method #3: Using dict.update()
Using dict.update() method, we can add an element to the dictionary, based on the condition if it exists or not.
Python3
# Python3 code to demonstrate working of# Multiply Dictionary Value by Constant# Using update() # Initialize dictionarytest_dict = {'gfg' : 1, 'is' : 2, 'for' : 4, 'CS' : 5} # printing original dictionaryprint("The original dictionary : " + str(test_dict)) # Initialize K K = 5 # Using update()# Multiply Dictionary Value by Constanttest_dict.update({'best' : test_dict.get('best', 1) * K}) # printing result print("Dictionary after the multiplication of key : " + str(test_dict)) |
The original dictionary : {'gfg': 1, 'is': 2, 'for': 4, 'CS': 5}
Dictionary after the multiplication of key : {'gfg': 1, 'is': 2, 'for': 4, 'CS': 5, 'best': 5}
Time complexity: O(1)
Auxiliary space: O(1)
