PySerial, How can I access a Port that is already open?

Question

I'm trying to control a relay module on an arduino via a pyython App.

I created a Class Relays as it goes :

class Relays():
def __init__(self, port="COM5", baudrate = 9600, parity=serial.PARITY_NONE, stopbit=serial.STOPBITS_ONE, bytesize = serial.EIGHTBITS):
    # self.commandlist=['?AV1\r','RT,ON\r','?RT\r']
    self.port=port
    self.baud=baudrate
    self.parity=parity
    self.stopbit=stopbit
    self.bytesize=bytesize
    self.ValveList = [['1','A'],['2','B'],['3','C'],['4','D'],['5','E'],['6','F'],['7','G'],['8','H']]

def open_port(self):
    try : 
        self.ser=serial.Serial(port=self.port,baudrate=self.baud)
    except:
        pass

def close_port(self):
    self.ser.close()
    print('port is close')
        
    
def Open_valve(self, n_valve):
    self.open_port()
    consign= self.ValveList[n_valve-1][0]#
    
    self.ser.write(consign.encode('utf8'))
 

So basically, in my app, I create an instance of the relay class : R=Relays() And this instance will be used by multiple other function to call the methods "Open_valve and "Close_valve"

My problem is when I want to create another instance of Relays() or when I restart my script (which means I need to recreate an instantce of Relays), the port is open so I cannot open it again.

I need to keep it open because if I don't, the relays will bee powered off, so I cannont close the port after each call of function. or use the syntax

with serial.Serial('COM5',9600) as ser:

Is there a way to find the serial port that is already open an use it ?

Thank you in advance, for your help !