`numpy:tri`

Signature

def tri(N, M = None, k = 0, dtype = <class 'float'>, *, like = None)

An array with ones at and below the given diagonal and zeros elsewhere.

N : int: Number of rows in the array.
M : int, optional: Number of columns in the array. By default, M is taken equal to N.
k : int, optional: The sub-diagonal at and below which the array is filled. k = 0 is the main diagonal, while k < 0 is below it, and k > 0 is above. The default is 0.
dtype : dtype, optional: Data type of the returned array. The default is float.
like : array_like, optional: Reference object to allow the creation of arrays which are not NumPy arrays. If an array-like passed in as like supports the __array_function__ protocol, the result will be defined by it. In this case, it ensures the creation of an array object compatible with that passed in via this argument.
versionadded 1.20.0

tri : ndarray of shape (N, M): Array with its lower triangle filled with ones and zero elsewhere; in other words T[i,j] == 1 for j <= i + k, 0 otherwise.

import numpy as np
np.tri(3, 5, 2, dtype=int)

✓

array([[1, 1, 1, 0, 0],
       [1, 1, 1, 1, 0],
       [1, 1, 1, 1, 1]])

np.tri(3, 5, -1)

✗

array([[0., 0., 0., 0., 0.],
       [1., 0., 0., 0., 0.],
       [1., 1., 0., 0., 0.]])