Here, we are first using the numpy.random.randint() function to create an nxn matrix that contains random integers. The generated random integers will be within the range [low, high). And the size argument specifies the size of the created matrix. For example, size=(n, n) specifies that the created matrix will have n rows and n columns.

Now, we are using the numpy.tril() function to create a lower triangular matrix from A. The argument k=0 specifies that all the elements above the principal diagonal will be made zero. And the elements across or below the principal diagonal are copied from A to the created lower triangular matrix.

The output of the mentioned program will be:

A: 
 [[5 5 6]
 [4 8 8]
 [9 2 3]]
The Lower Triangular Matrix L: 
 [[5 0 0]
 [4 8 0]
 [9 2 3]]