from mpmath import matrix

# Create a 3x3 matrix
A = matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

# Access the last element of the first row
print(A[0, -1])

I expect negative index -n to indicate last n element, like in Python list or numpy array. But I got 0.

After some digging, I found the related code:

The same goes for index of columns, such as A[-1,:] returns [0.0 0.0 0.0].

Are negative indices for other purposes? Can Python-like negative indices be supported?