Convert to binary and convert back to strings

[Hendrik van Rooyen]

 "Steven D'Aprano" <steve at REMOVE.THIS.cybersource.com.au> wrote:


> On Thu, 22 Feb 2007 08:18:07 +0200, Hendrik van Rooyen wrote:
>
> > I would xor each char in it with 'U' as a mild form of obfuscation...
>
> I've often wished this would work.
>
> >>> 'a' ^ 'U'
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: unsupported operand type(s) for ^: 'str' and 'str'
>
> instead of the more verbose
>
> >>> chr(ord('a') ^ ord('U'))
> '4'

you are not alone in this - to do something simple like calculating a BCC on a
string, or a checksum like at the end of a line in an Intel hex file is a bit of
a pain
in Python.

>
>
> > Look at the array module to get things you can xor, or use ord() on
> > each byte, and char()
>
> Arrays don't support XOR any more than strings do. What's the advantage to
> using the array module if you still have to jump through hoops to get it
> to work?

I think you will have less function calls, but I may be wrong:

s = 'some string that needs a bcc appended'
ar = array.array('B',s)
bcc = 0
for x in ar[:]:
    bcc ^= x
ar.append(bcc)
s=ar.tostring()

>
> ''.join([chr(ord(c) ^ 85) for c in text])
>
> is probably about as simple as you can get.
>

This is nice and compact.

It would be very nice if you could just use a single char string like
an int and apply the operators to it - the Python way seems so left-
handed - make it an int, do the work, make it back into a string -
and all the time we are working on essentially a one byte value...

- Hendrik