Intersection of Two Dictionaries via Keys in Python

Python / By Vikram Chiluka

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In Python, we will address the problem of intersecting two dictionaries via their keys. As a result, something in common between the two dictionaries is required.

You’ll come across a concept called Python dictionaries here. Dictionaries are a relatively prevalent data structure in the Python programming language.

Before going further into it, let us first talk about dictionaries.

Dictionaries:

Python dictionaries are mutable collections of things that contain key-value pairs. The dictionary contains two main components: keys and values. These keys must be single elements, and the values can be of any data type, such as list, string, integer, tuple, and so on. The keys are linked to their corresponding values. In other words, the values can be retrieved using their corresponding keys.

A dictionary is created in Python by enclosing numerous key-value pairs in curly braces.

Examples:

Example1:

Input:

dictionary1 = {'Hello': 'one', 'this': 'two', 'is': 'three', 'btechgeeks': 'four'} 
dictionary2 = {'good': 'five', 'morning': 'six', 'btechgeeks': 'four', 'is': 'three'}

Output:

The given first dictionary =  {'Hello': 'one', 'this': 'two', 'is': 'three', 'btechgeeks': 'four'}
The given second dictionary =  {'good': 'five', 'morning': 'six', 'btechgeeks': 'four', 'is': 'three'}
printing the intersection of the given two dictionaries =  {'is': 'three', 'btechgeeks': 'four'}

Example2:

Input:

dictionary1  = {'Hello': 'one', 'this': 'two', 'igs': 'three', 'btechgeeks': 'four'} 
dictionary2= {'good': 'five', 'hello': 'six', 'igs': 'three'}

Output:

The given first dictionary =  {'Hello': 'one', 'this': 'two', 'igs': 'three', 'btechgeeks': 'four'}
The given second dictionary =  {'good': 'five', 'hello': 'six', 'igs': 'three'}
printing the intersection of the given two dictionaries =  {'igs': 'three'}

Intersection of Two Dictionaries via Keys in Python

Below are the ways to find the intersection of two dictionaries via keys in Python.

Using Dictionary Comprehension
Using & Operator

Method #1: Using Dictionary Comprehension

Approach:

Give the two dictionaries as static input and store them in two variables.
Next, take dictionary1’s key as x and perform a for loop to see if the x in dictionary1 also exists in dictionary2. If it does, the common key and its value are moved to a new dictionary named intersectdicts.
Print the new dictionary intersectdicts with the common keys and their values.
The Exit of the Program.

Below is the implementation:

# Give the two dictionaries as static input and store them in two variables.
dictionary1 = {'Hello': 'one', 'this': 'two',
               'is': 'three', 'btechgeeks': 'four'}
dictionary2 = {'good': 'five', 'morning': 'six',
               'btechgeeks': 'four', 'is': 'three'}

# printing the original given two dictionaries
print("The given first dictionary = ", dictionary1)
print("The given second dictionary = ", dictionary2)
# Next, take dictionary1's key as k and perform a for loop
# to see if the k in dictionary1 also exists in dictionary2. If it does, the common key
# and its value are moved to a new dictionary named intersectdicts.
# intersection
intersectdicts = {k: dictionary1[k] for k in dictionary1 if k in dictionary2}

# Print the new dictionary intersectdicts with the common keys and their values.
print("printing the intersection of the given two dictionaries = ", (intersectdicts))

Output:

The given first dictionary =  {'Hello': 'one', 'this': 'two', 'is': 'three', 'btechgeeks': 'four'}
The given second dictionary =  {'good': 'five', 'morning': 'six', 'btechgeeks': 'four', 'is': 'three'}
printing the intersection of the given two dictionaries =  {'is': 'three', 'btechgeeks': 'four'}

Method #2: Using & Operator

Approach:

Give the two dictionaries as static input and store them in two variables.
Then, using the items() function, convert the dictionaries dictionary1 and dictionary2 into list format. Then, using the & operator, perform their AND operation. The common key-value pairs are then converted into a dictionary and stored in intersectdicts using dict().
Print the new dictionary intersectdicts with the common keys and their values.
The Exit of the Program.

Below is the implementation:

# Give the two dictionaries as static input and store them in two variables.
dictionary1 = {'Hello': 'one', 'this': 'two',
               'is': 'three', 'btechgeeks': 'four'}
dictionary2 = {'good': 'five', 'morning': 'six',
               'btechgeeks': 'four', 'is': 'three'}

# printing the original given two dictionaries
print("The given first dictionary = ", dictionary1)
print("The given second dictionary = ", dictionary2)
# Then, using the items() function,
# convert the dictionaries dictionary1 and dictionary2 into list format.
# Then, using the & operator, perform their AND operation.
# The common key-value pairs are then
# converted into a dictionary and stored in intersectdicts using dict().
intersectdicts = dict(dictionary1.items() & dictionary2.items())

# Print the new dictionary intersectdicts with the common keys and their values.
print("printing the intersection of the given two dictionaries = ", (intersectdicts))

Output:

The given first dictionary =  {'Hello': 'one', 'this': 'two', 'is': 'three', 'btechgeeks': 'four'}
The given second dictionary =  {'good': 'five', 'morning': 'six', 'btechgeeks': 'four', 'is': 'three'}
printing the intersection of the given two dictionaries =  {'is': 'three', 'btechgeeks': 'four'}

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