Plot a 2D graph from a .csv file with string format

There are many ways to do this, but I would choose this way if I were you.

with open('matrix.txt') as file:
    lines = file.read()
# lines: '1;2;3;,4;5;6;,7;8;9;,'

lines = [line.split(';') for line in lines.split(',')]
# lines: [['1', '2', '3', ''], ['4', '5', '6', ''], ['7', '8', '9', ''], ['']]

lines = [[float(value) for value in line if value] for line in lines]
lines = [line for line in lines if line]
# lines: [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0], [7.0, 8.0, 9.0]]

matrix = np.array(lines)
# matrix: array([[1., 2., 3.],
#                [4., 5., 6.],
#                [7., 8., 9.]])

Or, this way also could be your choice.

with open('matrix.txt') as file:
    lines = file.read()

lines = lines.replace(';', ' ').replace(',', ';')
# lines: '1 2 3 ;4 5 6 ;7 8 9 ;'

if lines[-1] == ';':
    lines = lines[:-1]

np.matrix(lines)

When saving your code, I think this would work too.

rm = np.genfromtxt('test.csv', delimiter=',', dtype='str', skip_header=26)
rm = np.array([[float(value) for value in line.split(';') if value] for line in rm])

They are not elegant, but they work.