Sending string to serial.to_bytes not working

Question

I am trying to send a string variable contains the command.

Like this:

value="[0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a]"
self.s.write(serial.to_bytes(value))

The above one fails. Won't give any error.

But it's working when I send a value like this:

self.s.write(serial.to_bytes([0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a]))

I also tried sending string like this:

self.s.write(serial.to_bytes(str(value)))

Still not working. Can someone please let me know how to send the value by storing in string?

I want to do this thing:

value="[0x"+anotherstring+",0x"+string2+"0x33, 0x0a]"

and send the value.

Thanks!

Answer 1

If passing a list of integers works for you then just convert your hexadecimal representations into integers and put them in a list.

Detailed steps:

1. Open a python interpreter

2. Import serialand open a serial port, call it ser.

3. Copy the code below and paste it in the python interpreter:

The code:

command = '310a320a330a'
hex_values = ['0x' + command[0:2],  '0x' + command[2:4],
              '0x' + command[4:6],  '0x' + command[6:8],
              '0x' + command[8:10], '0x' + command[10:12]]
int_values = [int(h, base=16) for h in hex_values]
ser.write(serial.to_bytes(int_values))

It will have the same effect that just this:

ser.write(serial.to_bytes([0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a]))

actually you can test that int_values == [0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a] is True so you are writing exactly the same thing.

Answer 2

serial.to_bytes takes a sequence as input. You should remove double quotes around value to pass a sequence of integers instead of a str representing the sequence you want to pass:

value = [0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a]
self.s.write(serial.to_bytes(value))  # works now

In the first case, you sent a sequence of bytes representing "[0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a]". Now, you will send the sequence [0x31, 0x0a, 0x32, 0x0a, 0x33, 0x0a] as expected.

---

If you want to send a string, just send it as bytes:

# Python 2
self.s.write('this is my string')
text = 'a string'
self.s.write(text)

# Python 3
self.s.write(b'this is my string')
text = 'a string'
self.s.write(text.encode())

And for a sequence:

for value in values:
    # Python 2
    self.s.write(value)

    # Python 3
    self.s.write(value.encode())