Python: How can I concatenate in a bytearray as I do with strings?

I would like to get part of a bytearray from a string or int but Python gives me an error.

I tried this calling sendfallblatt.self(1,02) as those code are selected in GUI with a combolist of texts linked to numbers.

    sendfallblatt(fallblattadresse, fallblattcode):

        # <BREAK> FF <COMMAND> <ADDR> < VALUE> 

        ComPort = serial.Serial('COM5')                 # open COM5
        ComPort.baudrate = 19200                # set Baud rate to 9600
        ComPort.bytesize = 8                    # Number of data bits = 8
        ComPort.parity   = 'N'                  # No parity
        ComPort.stopbits = 1                    # Number of Stop bits = 1
        
        data = bytearray(b'\xff\xc0\x0' + str(fallblattadresse) + '\x' + str(fallblattcode))
        print(data)
        
        ComPort.send_break(0.06)
        ComPort.write(data)
        ComPort.close()

And I was expecting to get :

data = bytearray(b'\xff\xc0\x01\x02')

fallblattadresse are from 0 to 7 and fallblattcode are from 0 to 61 so I know I will be having à problem after 9 but I will be solving that later...

Thanks for your help as I'm not finding anything useful on the internet and I'm probably missing some basic knowledge about bytes handling.

Solution

You're mixing up the representation of a byte array (which uses \x to show hex codes) and the actual byte values. You don't get a byte array by concatenating the string representations. You can use the bytes() function to create a byte array from a sequence of numeric byte values.

fallblattadresse, fallblattcode = 1, 2
data = bytearray(b'\xff\xc0' + bytes((fallblattadresse, fallblattcode)))
print(data)

prints

bytearray(b'\xff\xc0\x01\x02')

Unless you need to modify data after the concatenation, you don't need to convert it to a bytearray.