Python: Merge two Python dictionaries

Last update on April 21 2025 13:00:07 (UTC/GMT +8 hours)

8. Merge Two Python Dictionaries

Write a Python script to merge two Python dictionaries.

Sample Solution-1:

Python Code:

# Create the first dictionary 'd1' with key-value pairs.
d1 = {'a': 100, 'b': 200}

# Create the second dictionary 'd2' with key-value pairs.
d2 = {'x': 300, 'y': 200}

# Create a new dictionary 'd' and initialize it as a copy of 'd1'.
d = d1.copy()

# Update the dictionary 'd' by adding key-value pairs from 'd2'.
d.update(d2)

# Print the dictionary 'd' after combining the key-value pairs from 'd1' and 'd2.
print(d)

Sample Output:

{'x': 300, 'y': 200, 'a': 100, 'b': 200}

Sample Solution-2:

Create a new dict and loop over dicts, using dictionary.update() to add the key-value pairs from each one to the result.

Python Code:

# Define a function 'merge_dictionaries' that takes a variable number of dictionaries ('*dicts') as arguments.
# It merges the dictionaries into a new dictionary and returns the result.
def merge_dictionaries(*dicts):
    # Create an empty dictionary 'result' to store the merged key-value pairs.
    result = dict()

    # Iterate through the input dictionaries ('dicts') using a for loop.
    for d in dicts:
        # Update the 'result' dictionary by adding key-value pairs from the current dictionary 'd'.
        result.update(d)

    # Return the merged 'result' dictionary.
    return result

# Create two dictionaries 'students1' and 'students2' with key-value pairs.
students1 = {
    'Theodore': 10,
    'Mathew': 11,
}

students2 = {
    'Roxanne': 9
}

# Print a message indicating the start of the code section.
print("Original dictionaries:")

# Print the original dictionaries 'students1' and 'students2'.
print(students1)
print(students2)

# Print a message indicating the start of the merged dictionaries section.
print("\nMerge dictionaries:")

# Call the 'merge_dictionaries' function with 'students1' and 'students2' as arguments to merge the dictionaries.
# Print the result, which is the merged dictionary.
print(merge_dictionaries(students1, students2))

Sample Output:

Original dictionaries:
{'Theodore': 10, 'Mathew': 11}
{'Roxanne': 9}

Merge dictionaries:
{'Theodore': 10, 'Mathew': 11, 'Roxanne': 9}

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python script to merge two dictionaries and handle overlapping keys by taking the value from the second dictionary.
Write a Python script to merge two dictionaries using the unpacking operator (**) and print the result.
Write a Python script to merge two dictionaries recursively when keys map to sub-dictionaries.
Write a Python script to combine dictionaries and, in case of key collisions, concatenate their values if they are strings.

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