Python - decode('hex')

[MRAB]

On 2017-02-20 19:43, Ganesh Pal wrote:
> On Feb 21, 2017 12:17 AM, "Rhodri James" <rhodri at kynesim.co.uk> wrote:
>
> On 20/02/17 17:55, Ganesh Pal wrote:
>
>> 1. The only difference between both the programs  the difference are just
>> the below lines.
>>
>> newdata = '64000101057804'.decode('hex')
>>
>>         and
>>
>> newdata = ""
>> newdata = '64000101057804'
>> newdata.decode('hex')
>>
>>
>> What is happening here and how do I fix this in  program 2  ?   for my eyes
>> there doesn't look any difference .
>>
>
> Python strings are immutable; methods like decode() create a brand new
> string for you.  What your program 2 version does is to name the string of
> hex digits "newdata", decode it as hex into a new string and then throw
> that new string away.  Your program 1 version by contrast decodes the
> string of digits as hex and then names is "newdata", throwing the original
> string of digits away
>
>
> Thanks for the reply James.
>
> How can I make my program 2 look like program 1 ,  any hacks ? because I
> get newdata value( as a hx return value Of type string  )from a function.
>
In this:

     newdata.decode('hex')

The .decode method doesn't change newdata in-place, it _returns_ the result.

You're doing anything with that result. You're not binding (assigning) 
it to a name. You're not passing it into a function. You're not doing 
_anything_ with it. You're just letting it be discarded, thrown away.

You could ask the user for the hex string:

     hex_string = raw_input('Enter the hex string: ')

and then decode it:

     newdata = hex_string.decode('hex')