Python - Intersect two dictionaries through keys

In Python, intersecting two dictionaries through keys means creating a new dictionary containing only the keys that exist in both dictionaries. This is useful for finding common data between two datasets.

Input:
dict_1 = {'A': 1, 'B': 2, 'C': 3}
dict_2 = {'A': 1, 'C': 4, 'D': 5}

Output:
{'A': 1, 'C': 3}

Using Dictionary Comprehension

Dictionary comprehension provides the most readable approach to intersect dictionaries by keys ?

# initializing the dictionaries
dict_1 = {'A': 1, 'B': 2, 'C': 3}
dict_2 = {'A': 1, 'C': 4, 'D': 5}

# finding the common keys
result = {key: dict_1[key] for key in dict_1 if key in dict_2}

# printing the result
print(result)

{'A': 1, 'C': 3}

This method keeps values from the first dictionary (dict_1) for all common keys.

Using Set Intersection with Keys

You can use set operations to find common keys, then build the result dictionary ?

# initializing the dictionaries
dict_1 = {'A': 1, 'B': 2, 'C': 3}
dict_2 = {'A': 1, 'C': 4, 'D': 5}

# finding common keys using set intersection
common_keys = dict_1.keys() & dict_2.keys()
result = {key: dict_1[key] for key in common_keys}

# printing the result
print(result)

{'A': 1, 'C': 3}

Using Bitwise AND on Items

The bitwise AND operator on dictionary items filters key-value pairs that are identical in both dictionaries ?

# initializing the dictionaries
dict_1 = {'A': 1, 'B': 2, 'C': 3}
dict_2 = {'A': 1, 'C': 4, 'D': 5}

# finding identical key-value pairs
result = dict(dict_1.items() & dict_2.items())

# printing the result
print(result)

{'A': 1}

Note: This method only includes keys where both the key AND value are identical in both dictionaries. Key 'C' is excluded because it has different values (3 vs 4).

Comparison

Conclusion

Use dictionary comprehension for general key intersection. Use bitwise AND on items when you need identical key-value pairs. Both methods are efficient for intersecting dictionaries based on your specific requirements.