Python – Replace dictionary value from other dictionary

Given two dictionaries, update the values from other dictionary if key is present in other dictionary.

Input : test_dict = {“Gfg” : 5, “is” : 8, “Best” : 10, “for” : 8, “Geeks” : 9},
updict = {“Geeks” : 10, “Best” : 17}
Output : {‘Gfg’: 5, ‘is’: 8, ‘Best’: 17, ‘for’: 8, ‘Geeks’: 10}
Explanation : “Geeks” and “Best” values updated to 10 and 17.

Input : test_dict = {“Gfg” : 5, “is” : 8, “Best” : 10, “for” : 8, “Geeks” : 9},
updict = {“Geek” : 10, “Bet” : 17}
Output : {‘Gfg’: 5, ‘is’: 8, ‘Best’: 10, ‘for’: 8, ‘Geeks’: 9}
Explanation : No values matched, hence original dictionary.

Method #1 : Using loop 

This is brute way in which this task can be performed. In this, we run a loop for each key in target dictionary and update in case the value is present in other dictionary.

Python3

# Python3 code to demonstrate working of
# Replace dictionary value from other dictionary
# Using loop

# initializing dictionary
test_dict = {"Gfg" : 5, "is" : 8, "Best" : 10, "for" : 8, "Geeks" : 9}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# initializing updict
updict = {"Gfg"  : 10, "Best" : 17}

for sub in test_dict:

    # checking if key present in other dictionary
    if sub in updict:
        test_dict[sub]  = updict[sub]

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

Output

The original dictionary is : {‘Gfg’: 5, ‘is’: 8, ‘Best’: 10, ‘for’: 8, ‘Geeks’: 9}
The updated dictionary: {‘Gfg’: 10, ‘is’: 8, ‘Best’: 17, ‘for’: 8, ‘Geeks’: 9}

Method #2 : Using dictionary comprehension

This is one liner approach in which this task can be performed. In this, we iterate for all the dictionary values and update in a one-liner manner in dictionary comprehension.

Python3

# Python3 code to demonstrate working of
# Replace dictionary value from other dictionary
# Using dictionary comprehension

# initializing dictionary
test_dict = {"Gfg" : 5, "is" : 8, "Best" : 10, "for" : 8, "Geeks" : 9}

# printing original dictionary
print("The original dictionary is : " + str(test_dict))

# initializing updict
updict = {"Gfg"  : 10, "Best" : 17}

res = {key: updict.get(key, test_dict[key]) for key in test_dict}

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

Output

The original dictionary is : {‘Gfg’: 5, ‘is’: 8, ‘Best’: 10, ‘for’: 8, ‘Geeks’: 9}
The updated dictionary: {‘Gfg’: 10, ‘is’: 8, ‘Best’: 17, ‘for’: 8, ‘Geeks’: 9}