numpy.tril(a, k=0) : Returns copy of array with lower part of the triangle w.r.t k Parameters :

a : input array
k : [int, optional, 0 by default]
          Diagonal we require; k>0 means diagonal above main diagonal or vice versa.

Returns :

Lower triangle of a, having same shape and data-type as a.

Python

# Python Programming illustrating
# numpy.tril method

import numpy as geek

# string input
a = geek.matrix([[1, 21, 30], 
                 [63 ,434, 3], 
                 [54, 54, 56]])

print("Main Diagonal elements : \n", geek.tril(a), "\n")

print("Diagonal above main Diagonal elements : \n", geek.tril(a, 1), "\n\n")

print("Main Diagonal elements : \n", geek.tril(a, -1))

Output :

Main Diagonal elements : 
 [[  1   0   0]
 [ 63 434   0]
 [ 54  54  56]] 

Diagonal above main Diagonal elements : 
 [[  1  21   0]
 [ 63 434   3]
 [ 54  54  56]] 


Main Diagonal elements : 
 [[ 0  0  0]
 [63  0  0]
 [54 54  0]]

References: https://numpy.org/doc/stable/reference/generated/numpy.tril.html#numpy.tril Note : These NumPy-Python programs won't run on online IDE's, so run them on your systems to explore them .