How to check if all values in the columns of a NumPy matrix are the same?

Learn, how to check if all values in the columns of a NumPy matrix are the same in Python? By Pranit Sharma Last updated : December 23, 2023

NumPy is an abbreviated form of Numerical Python. It is used for different types of scientific operations in python. Numpy is a vast library in python which is used for almost every kind of scientific or mathematical operation. It is itself an array which is a collection of various methods and functions for processing the arrays.

Problem statement

Suppose that we are given a NumPy array that mostly contains similar values, we need to check if all values in the columns of a numpy matrix are the same or not.

Checking if all values in the columns of a NumPy matrix are the same

For this purpose, we can compare each value to the corresponding value in the first row and a column shares a common value if all the values in that column are True.

To check whether all values in the rows of a NumPy matrix are the same or not: Use arr == arr[0,:]
To check whether all values in the columns of a NumPy matrix are the same or not: Use np.all(arr == arr[0,:], axis = 0)

Thus, you can use numpy.all() method to compare all values column-wise.

Let us understand with the help of an example,

Python code to check if all values in the columns of a NumPy matrix are the same

# Import numpy
import numpy as np

# Creating a numpy array
arr = np.array([[1,1,0],[1,-1,0],[1,0,0],[1,1,0]])

# Display original array
print("Original Array:\n",arr,"\n")

# Checking all rows
res = arr == arr[0,:]

# Display row result
print("Rows result:\n",res,"\n")

# Checking for columns
res = np.all(arr == arr[0,:], axis = 0)

# Display result
print("Result:\n",res,"\n")