import serial
port = 'COM1'

ser = serial.Serial()
ser.port=port
ser.baudrate=9600
ser.open()
ser.write(b'q')
ser.close()

Traceback (most recent call last):
  File "C:UsersMateuszDesktopserialpy.py", line 7, in <module>
    ser.open()
  File "C:Python37libsite-packagesserialserialwin32.py", line 62, in open
    raise SerialException("could not open port {!r}: {!r}".format(self.portstr, ctypes.WinError()))
serial.serialutil.SerialException: could not open port 'COM1': FileNotFoundError(2, 'The system cannot find the file specified.', None, 2)