Python | Intersection of two lists
Intersection of two list means we need to take all those elements which are common to both of the initial lists and store them into another list. Now there are various ways in Python, through which we can perform the Intersection of the lists.
Examples:
Method 1:
This is the simplest method where we haven’t used any built-in functions.
|
# Python program to illustrate the intersection
# of two lists in most simple way
def intersection(lst1, lst2):
lst3 = [value for value in lst1 if value in lst2]
return lst3
# Driver Code
lst1 = [4, 9, 1, 17, 11, 26, 28, 54, 69]
lst2 = [9, 9, 74, 21, 45, 11, 63, 28, 26]
print(intersection(lst1, lst2))
|
Output:
Method 2:
This method includes the use of set() method.
|
# Python program to illustrate the intersection
# of two lists using set() method
def intersection(lst1, lst2):
return list(set(lst1) & set(lst2))
# Driver Code
lst1 = [15, 9, 10, 56, 23, 78, 5, 4, 9]
lst2 = [9, 4, 5, 36, 47, 26, 10, 45, 87]
print(intersection(lst1, lst2))
|
Output:
Method 3:
In this method we set() the larger list and then use the built-in function called intersection() to compute the intersected list. intersection() is a first-class part of set.
|
# Python program to illustrate the intersection
# of two lists using set() and intersection()
def Intersection(lst1, lst2):
return set(lst1).intersection(lst2)
# Driver Code
lst1 = [ 4, 9, 1, 17, 11, 26, 28, 28, 26, 66, 91]
lst2 = [9, 9, 74, 21, 45, 11, 63]
print(Intersection(lst1, lst2))
|
Output:
Method 4:
By the use of this hybrid method the complexity of the program falls to O(n). This is an efficient way of doing the following program.
|
# Python program to illustrate the intersection
# of two lists
def intersection(lst1, lst2):
# Use of hybrid method
temp = set(lst2)
lst3 = [value for value in lst1 if value in temp]
return lst3
# Driver Code
lst1 = [9, 9, 74, 21, 45, 11, 63]
lst2 = [4, 9, 1, 17, 11, 26, 28, 28, 26, 66, 91]
print(intersection(lst1, lst2))
|
Output:
Method 5:
This is the where the intersection is performed over sub-lists inside other lists. Here we have used the concept of filter().
|
# Python program to illustrate the intersection
# of two lists, sublists and use of filter()
def intersection(lst1, lst2):
lst3 = [list(filter(lambda x: x in lst1, sublist)) for sublist in lst2]
return lst3
# Driver Code
lst1 = [1, 6, 7, 10, 13, 28, 32, 41, 58, 63]
lst2 = [[13, 17, 18, 21, 32], [7, 11, 13, 14, 28], [1, 5, 6, 8, 15, 16]]
print(intersection(lst1, lst2))
|
Working: The filter part takes each sublist’s item and checks to see if it is in the source list. The list comprehension is executed for each sublist in list2.
Output:
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Python | Union of two or more Lists
Union of a list means, we must take all the elements from list A and list B (there can be more than two lists) and put them inside a single new list. There are various orders in which we can combine the lists. For e.g., we can maintain the repetition and order or remove the repeated elements in the final list and so on.
Examples:
Python Program Find Union and Intersection of Two Arrays
- Algorithm to find union and intersection of two arrays
- Python program to find union and intersection of two arrays
Algorithm to find union and intersection of two arrays
- First of all, Take two lists from the user.
- Take thebitwise or (|)between the sets of both arrays to find union and assign it into a variableXin the form of lists.
- To find the intersection of between two arrays, use thebitwise and (&)between the sets of given arrays and assign it into a variableYin the form of lists.
- Print variableXandYwhich is our required output.
Python program to find union and intersection of two arrays
Use the following steps to write a python program to find union and intersection of two arrays:
- Take input Two arrays from the user in the program.
- Find the union and intersection of these arrays bitwise operators.
- Store result in different variables.
- Print result.
After executing the program, the output will be:
Enter elements of first list: 2 5 6 Enter elements of second list: 5 7 9 6 Union of the arrays: [2, 5, 6, 7, 9] intersection of the arrays: [5, 6]Find the union and intersection of two arrays in Python
Here, we are going to learn how to find the union and intersection of two arrays in Python programming language?
Submitted by Bipin Kumar, on October 25, 2019
Two arrays will be given by the user and we have to find the union and intersection of these arrays in the Python programming. To find the union and intersection of these arrays, we will use the bitwise or (|) and bitwise and (&) respectively between the set of the given arrays. Before going to solve this problem we will learn about the union and intersection.
Union and intersection of two arrays
A list that has the common distinct element from both arrays and if there are repetitions of the element then only one occurrence is considered, known as the union of both arrays.
A list that has common distinct elements from both arrays, is the intersection of both arrays.
Algorithm to solve this problem
- Initially, we will take two lists from the user which may have repeated numbers or not.
- We will take the bitwise or (|) between the sets of both arrays to find union and assign it into a variable A in the form of lists.
- To find the intersection of both arrays, we will use the bitwise and (&) between the sets of given arrays and assign it into a variable B in the form of lists.
- Print variable A and B which is our required output.
Let's start writing the Python program by the implementation of the above algorithm.
Code:
a=list(map(int,input('Enter elements of first list:').split())) b=list(map(int,input('Enter elements of second list:').split())) A=list(set(a)|set(b)) B=list(set(a)&set(b)) print('Union of the arrays:',A) print('intersection of the arrays:',B)Output
Enter elements of first list: 3 4 6 4 4 6 7 41 Enter elements of second list: 78 3 5 7 -1 9 2 -5 Union of the arrays: [2, 3, 4, 5, 6, 7, 41, 9, 78, -5, -1] intersection of the arrays: [3, 7]set() function is inbuilt in Python which is used to convert a list into another list which does not contain duplicate or repeated elements.
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Python Program to Find Intersection of Two Lists
In this tutorial, we will discuss how we can get the intersection of the two lists. The intersection of two lists means we need to get all the familiar elements to both of the initial lists.
Python is known for its excellent built-in data structure. Python list is one of the famous and valuable built-in data types of Python. It can store the various data-types value in sorted order. However, there is no built-in function for lists like sets.
Python provides the many ways to perform the intersection of the lists. Let's see the following scenario.
Input :
Output:
Input :
Output:
Let's see following methods to get intersection of two lists.
Method - 1: Using for loop
Output:
We have used for loop to get the common value from both lists and stored it in the list3 variable.
Method - 2: Convert List to Set
Output:
Method - 3:
We will use the built-in set's intersection() method. The intersection() is a first-class part of the set. Let's understand the following example.
Example -
Output:
Method - 4:
In this method, we will use the hybrid method. This is much efficient way to perform the task. Let's understand the following example.
Example -
Output:
Method - 5:
In this method, we will use the filter() method. The intersection is performed over sub-lists inside other lists. Let's understand the following example.
Example -
Output:
The filter() method takes each item of the sublist and checks if it is present in the list1. The list comprehension is executed for each sublist in the list2.
How to find the intersection and union of two lists in Python
My friend Bill had previously alerted me to the coolness of Python sets. However I hadn't found opportunity to use them until now. Here are three functions using sets to remove duplicate entries from a list, find the intersection of two lists, and find the union of two lists. Note, sets were introduced in Python 2.4, so Python 2.4 or later is required. Also, the items in the list must be hashable and order of the lists is not preserved.
For more information on Python sets, see the Library Reference.
Results:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] [8, 9, 5, 6, 7] [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]