print a 2d matrix diagonally

print_diag.py

def print_diag(matrix):
    h = len(matrix)
    w = len(matrix[0])

    x = 0
    y = 0
    anchor = 0
    while True:
        if x >= w or y < 0:
            anchor += 1
            y = anchor
            x = 0
            print
        if anchor >= h:
            break
        print matrix[y][x],
        y -= 1
        x += 1

    anchor = 1
    x = 1
    y = h - 1
    while True:
        if x >= w or y < 0:
            anchor += 1
            x = anchor
            y = h - 1
            print
        if anchor >= w:
            break
        print matrix[y][x],
        y -= 1
        x += 1

print_diag([[1, 2, 3],
            [4, 5, 6],
            [7, 8, 9],
            [10, 11, 12]])