[Tutor] string to binary and back... Python 3

[Dave Angel]

On 07/18/2012 05:07 PM, Jordan wrote:
> OK so I have been trying for a couple days now and I am throwing in the
> towel, Python 3 wins this one.
> I want to convert a string to binary and back again like in this
> question: Stack Overflow: Convert Binary to ASCII and vice versa
> (Python)
> <http://stackoverflow.com/questions/7396849/convert-binary-to-ascii-and-vice-versa-python>
> But in Python 3 I consistently get  some sort of error relating to the
> fact that nothing but bytes and bytearrays support the buffer interface
> or I get an overflow error because something is too large to be
> converted to bytes.
> Please help me and then explian what I am not getting that is new in
> Python 3. I would like to point out I realize that binary, hex, and
> encodings are all a very complex subject and so I do not expect to
> master it but I do hope that I can gain a deeper insight. Thank you all.
>
> test_script.py:
> import binascii
>
> test_int = 109
>
> test_int = int(str(test_int) + '45670')
> data = 'Testing XOR Again!'
>
> while sys.getsizeof(data) > test_int.bit_length():
>
> test_int = int(str(test_int) + str(int.from_bytes(os.urandom(1), 'big')))
>
> print('Bit Length: ' + str(test_int.bit_length()))
>
> key = test_int # Yes I know this is an unnecessary step...
>
> data = bin(int(binascii.hexlify(bytes(data, 'UTF-8')), 16))
>
> print(data)
>
> data = int(data, 2)
>
> print(data)
>
> data = binascii.unhexlify('%x' % data)
>

I don't get the same error you did.  I get:

 File "jordan.py", line 13
    test_int = int(str(test_int) + str(int.from_bytes(os.urandom(1),
'big')))
           ^
IndentationError: expected an indented block


Please post it again, with correct indentation.  if you used tabs, then
expand them to spaces before pasting it into your test-mode mail editor.


I'd also recommend you remove a lot of the irrelevant details there.  if
you have a problem with hexlfy and/or unhexlify, then give a simple byte
string that doesn't work for you, and somebody can probably identify why
not.  And if you want people to run your code, include the imports as well.

As it is, you're apparently looping, comparing the byte memory size of a
string (which is typically 4 bytes per character) with the number of
significant bits in an unrelated number.

I suspect what you want is something resembling (untested):

    mybytes = bytes( "%x" % data, "ascii")
    newdata = binascii.unexlify(mybytes)


-- 
DaveA