Python serial: how to add CR, LF(\r\n) to message?

Question

Python

Hello ! For example, there is a number: I need to pass it to the serial port as an ascii string. Not a symbol corresponding to a digit, but to form a string of digits, that is, a string consisting of just hex digits should go to the port, this is how it should look: If we listen to the serial port, for example, via putty, we will see plain text there 03E8 :
input = 0x3E8

input = 0x3E8
str_res = binascii.b2a_hex(input.to_bytes(2, "big"))

#to upper case
for e in str_res:
   arr_for_send.append( ord(chr(e).upper()) )

#send to serial 
ser.write(serial.to_bytes(arr_for_send))

Everything seems to be working. But, each message must end.
\r\n

I do it like this:

input = 0x3E8
str_res = binascii.b2a_hex(input.to_bytes(2, "big"))

#add CR LF
arr_for_send.append(ord('\r'))
arr_for_send.append(ord('\n'))

#to upper case
for e in str_res:
   arr_for_send.append( ord(chr(e).upper()) )

#send to serial 
ser.write(serial.to_bytes(arr_for_send))

The log analyzer sees the following result:


At the same time, if you try to send in an endless loop with a short pause:

while 1:
   ser.write(serial.to_bytes(arr_for_send))
   time.sleep(.3)

PS I'm testing sending via cp2102