Python – Update dictionary with other dictionary

Sometimes, while working with Python dictionaries, we can have problem in which we need to perform the update of dictionary with other keys of dictionary. This can have applications in domains in which we need to add certain records to previously captured records. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using loop
This is a brute force way in which this task can be performed. In this, we check for keys in other dictionary, and add the items in new dictionary.

# Python3 code to demonstrate working of
# Update dictionary with other dictionary
# Using loop

# initializing dictionaries
test_dict1 = {'gfg' : 1, 'best' : 2, 'for' : 4, 'geeks' : 6}
test_dict2 = {'for' : 3, 'geeks' : 5}

# printing original dictionaries
print("The original dictionary 1 is : " + str(test_dict1))
print("The original dictionary 2 is : " + str(test_dict2))

# Update dictionary with other dictionary
# Using loop
for key in test_dict1:
    if key in test_dict2:
        test_dict1[key] = test_dict2[key]

# printing result
print("The updated dictionary is : " + str(test_dict1))

Output :

The original dictionary 1 is : {‘best’: 2, ‘for’: 4, ‘gfg’: 1, ‘geeks’: 6}
The original dictionary 2 is : {‘for’: 3, ‘geeks’: 5}
The updated dictionary is : {‘best’: 2, ‘for’: 3, ‘gfg’: 1, ‘geeks’: 5}

Method #2 : Using dictionary comprehension
This is yet another way in which this task can be performed. In this, we iterate for dictionary and perform update in single line using comprehension.

# Python3 code to demonstrate working of
# Update dictionary with other dictionary
# Using dictionary comprehension

# initializing dictionaries
test_dict1 = {'gfg' : 1, 'best' : 2, 'for' : 4, 'geeks' : 6}
test_dict2 = {'for' : 3, 'geeks' : 5}

# printing original dictionaries
print("The original dictionary 1 is : " + str(test_dict1))
print("The original dictionary 2 is : " + str(test_dict2))

# Update dictionary with other dictionary
# Using dictionary comprehension
res = {key : test_dict2.get(key, val)  for key, val in test_dict1.items()}

# printing result
print("The updated dictionary is : " + str(res))

Output :

The original dictionary 1 is : {‘best’: 2, ‘for’: 4, ‘gfg’: 1, ‘geeks’: 6}
The original dictionary 2 is : {‘for’: 3, ‘geeks’: 5}
The updated dictionary is : {‘best’: 2, ‘for’: 3, ‘gfg’: 1, ‘geeks’: 5}