How to add two dictionaries in python with same keys

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Dictionary is a collection which is unordered, changeable and indexed. In Python, dictionaries are written with curly brackets, and they have keys and values. It is widely used in day to day programming, web development, and machine learning. Combining dictionaries is very common task in operations of dictionary.

Let’s see how to combine the values of two dictionaries having same key.

Method #1: Using Counter
Counter is a special subclass of dictionary which performs acts same as dictionary in most cases.

from collections import Counter

ini_dictionary1 = Counter({'nikhil': 1, 'akash' : 5,

                     'manjeet' : 10, 'akshat' : 15})

ini_dictionary2 = Counter({'akash' : 7, 'akshat' : 5,

                                          'm' : 15})

print ("initial 1st dictionary", str(ini_dictionary1))

print ("initial 2nd dictionary", str(ini_dictionary2))

final_dictionary = ini_dictionary1 + ini_dictionary2

print ("final dictionary", str(final_dictionary))

Output:

initial 1st dictionary Counter({‘akshat’: 15, ‘manjeet’: 10, ‘akash’: 5, ‘nikhil’: 1})
initial 2nd dictionary Counter({‘m’: 15, ‘akash’: 7, ‘akshat’: 5})
final dictionary Counter({‘akshat’: 20, ‘m’: 15, ‘akash’: 12, ‘manjeet’: 10, ‘nikhil’: 1})

 
Method #2: Using dict() and items
This method is for Python version 2.

ini_dictionary1 = {'nikhil': 1, 'akash' : 5,

              'manjeet' : 10, 'akshat' : 15}

ini_dictionary2 = {'akash' : 7, 'akshat' : 5,

                                    'm' : 15}

print ("initial 1st dictionary", str(ini_dictionary1))

print ("initial 2nd dictionary", str(ini_dictionary2))

final_dictionary = dict(ini_dictionary1.items() + ini_dictionary2.items() +

                    [(k, ini_dictionary1[k] + ini_dictionary2[k])

                    for k in set(ini_dictionary2)

                    & set(ini_dictionary1)])

print ("final dictionary", str(final_dictionary))

Output:

(‘initial 1st dictionary’, “{‘manjeet’: 10, ‘nikhil’: 1, ‘akshat’: 15, ‘akash’: 5}”)
(‘initial 2nd dictionary’, “{‘m’: 15, ‘akshat’: 5, ‘akash’: 7}”)
(‘final dictionary’, “{‘nikhil’: 1, ‘m’: 15, ‘manjeet’: 10, ‘akshat’: 20, ‘akash’: 12}”)

 
Method #3: Using dict comprehension and set

ini_dictionary1 = {'nikhil': 1, 'akash' : 5, 

              'manjeet' : 10, 'akshat' : 15}

ini_dictionary2 = {'akash' : 7, 'akshat' : 5, 

                                    'm' : 15}

print ("initial 1st dictionary", str(ini_dictionary1))

print ("initial 2nd dictionary", str(ini_dictionary2))

final_dictionary =  {x: ini_dictionary1.get(x, 0) + ini_dictionary2.get(x, 0)

                    for x in set(ini_dictionary1).union(ini_dictionary2)}

print ("final dictionary", str(final_dictionary))

Output:

initial 1st dictionary {‘nikhil’: 1, ‘akshat’: 15, ‘akash’: 5, ‘manjeet’: 10}
initial 2nd dictionary {‘akshat’: 5, ‘akash’: 7, ‘m’: 15}
final dictionary {‘nikhil’: 1, ‘akshat’: 20, ‘akash’: 12, ‘m’: 15, ‘manjeet’: 10}