Encoding passed argument for serial.write python

Question

I am trying to send some data by an xbee from pc to arduino.

I have a test packet which I know it well built which is:

7E 00 7D 33 10 01 00 7D 33 A2 00 40 69 76 DD FF FE 00 00 01 52 B8 DA 41 1A

If I use:

ser.write(b'\x7E\x00\x7D\x33\x10\x01\x00\x7D\x33\xA2\x00\x40\x69\x76\xDD\xFF\xFE\x00\x00\x01\x52\xB8\xDA\x41\x1A')

My packet arrives to arduino.

But now I want to pass this packet by command line. Something like:

python test.py '\x7E\x00\x7D\x33\x10\x01\x00\x7D\x33\xA2\x00\x40\x69\x76\xDD\xFF\xFE\x00\x00\x01\x52\xB8\xDA\x41\x1A'

Being able this way to change data every time I want.

I tried with:

ser.write(sys.argv[1])
ser.write(sys.argv[1].encode('ascii'))

And other tries but always fails.

Any idea about how I have to pass the data? I think the problem is related to the initial b in ser.write...

I am using python 2.6 or 2.7... Not 3.

Answer 1

This works, but I have a feeling there's a better solution ^{(there was; see the edit)} :

import ast
import sys

ser.write(ast.literal_eval("'{0}'".format(sys.argv[1])))

We use the safe literal_eval from the ast module to evaulate the string "'\\x7E\\x00\\x7D...'" as a python literal, which gets us what we want.

EDIT: Ah- hah! Found a better solution here :

ser.write(sys.argv[1].decode("string-escape"))