使用转义字符'\\ x'创建字符串并在python中输入用户

Question

I am trying to create a string with user input with '\\x' escape character

I am doing something like this -

    def create_hex_string(a, b): # a and b are integers of range (0-255)
        # convert decimal to hex and pad it with 0
        # for eg: 10 -> 0x0a
        ahex = "{0:#0{1}x}".format(register,4)
        bhex = "{0:#0{1}x}".format(value,4)
        str = "\x08\x{}\x00\x{}".format(ahex[2:], bhex[2:])
        return str

When I try to execute this, the escape characters are no more relevant and it gives me an error.

I also tried to use literal strings to create my hex string with user inputs, something like -

str = r'\x08\x{}\x00\x{}'.format(ahex[2:], bhex[2:])

But I don't find a way to convert a literal string back to a non literal one which can identify the escape characters.

I also tried to see how re.escape() works, but it escapes all characters except ASCII. Any pointers regarding this would be really appreciated.

---

Better explanation

I have a peripheral hardware device with registers. I can set a specific value in a specific register in the device over a socket.

sock.send("\x80\x01")

This command only works if it is a double quoted string, so the \\x escape character has a meaning. The command above would set register 128 to value 1 because- 0x80 = 128 0x01 = 1

On that line of thought, I created a function

1   def create_hex_string(register, value): # a and b are integers of range (0-255)
2       # funky stuff to convert register and value to hex.
3       # reghex = hex value of register (128 = 80 in hex)
4       # valhex = hex value of value (1 = 01 in hex)
5       str = "\x{}\x{}".format(reghex, valhex)
6   return str

7   cmd = create_hex_string(128, 1)
8   sock.send(cmd)

If you see, line 5 would give an error, it does not accept. Instead of double quoted string in line 7, I used a literal string with format.

5    str = r'\x{}\x{}'.format(reghex, valhex)

With this I lost the significance of the escape characters.

I hope this helps to understand the problem better. Let me if I missed something, and I will add that in the next edit.

Answer 1

You can create a one-character string from a integer value using the chr() function.

Is this what you are trying to do?

def create_hex_string(a, b): # a and b are integers of range (0-255)
    return "\x08{}\x00{}".format(chr(a), chr(b))

s = create_hex_string(65, 66)
assert s[0] == '\x08'
assert s[1] == 'A'
assert s[2] == '\x00'
assert s[3] == 'B'
assert s == "\x08\x41\x00\x42"

# The example from OP's comment:
assert create_hex_string(128, 1) == "\x08\x80\x00\x01"