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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.
Python Array Programs »
Created: May-24, 2021 This tutorial will introduce the
methods to perform intersection on NumPy arrays in Python. Intersection means the common elements in two sets of elements. If we want to find the intersection of two 1D NumPy arrays, we can use the numpy.in1d[] Method in Pythonnumpy.intersect1d[] Method in PythonNumPy Intersection With the
numpy.in1d[] Method in Pythonnumpy.in1d[] method in Python. The numpy.in1d[] method takes the two arrays, checks
whether each element of the first array is present in the second array, and returns a boolean array that contains true for each element present in both arrays and false for each element present in the first array but not in the second array. We can use this resultant array as the first array index to get the common elements in both arrays.
import numpy as np
A = np.array[[2,3,5,7,11]]
B = np.array[[1,3,5,7,9]]
C = A[np.in1d[A, B]]
print[C]
Output:
[3 5 7]
We first created the two arrays with the np.array[] method. We then stored the intersection of both arrays inside array
C with C = A[np.in1d[A, B]].
NumPy Intersection With the numpy.intersect1d[] Method in Python
We can also use the numpy.intersect1d[] method to find the intersection of two 1D arrays in Python. The numpy.intersect1d[] method takes the arrays and returns the sorted intersection in the form
of another 1D array. See the following code example.
import numpy as np
A = np.array[[2,3,5,7,11]]
B = np.array[[1,3,5,7,9]]
C = np.intersect1d[A, B]
print[C]
Output:
[3 5 7]
We stored the intersection of arrays A and B inside array C with the numpy.intersect1d[] method in the above code.
Both methods work just fine, but the np.intersect1d[] method is easier to use than the np.in1d[] method.