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

[Mark Lawrence]

On 19/07/2012 06:41, wolfrage8765 at gmail.com wrote:
> On Thu, Jul 19, 2012 at 12:16 AM, Dave Angel <d at davea.name> wrote:
>
>>   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')))
>>             ^
>>
> test_int = int(str(test_int) + str(int.from_bytes(os.urandom(1), \
>      'big')))
> # That was probably just do to the copy and paste.
>
>> 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 only use spaces and this program did not require any indentation until
> it was pasted and the one line above became split across two line. Really
> though that was a trivial error to correct.

Really?  Are you using a forked version of Python that doesn't need 
indentation after a while loop, or are you speaking with a forked 
tongue? :)  Strangely I believe the latter, so please take note of what 
Dave Angel has told you and post with the correct indentation.

>
>>
>> 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.
>>
>> My problem is not specific to hexlify and unhexlify, my problem is trying
> to convert from string to binary and back. That is why all of the details,
> to show I have tried on my own.
> Sorry that I forgot to include sys and os for imports.
>
>
>> 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)
>>
>> I was comparing them but I think I understand how to compare them well,
> now I want to convert them both to binary so that I can XOR them together.
> Thank you for your time and help Dave, now I need to reply to Ramit.
>
>>
>> --
>> DaveA
>>
>
>
>
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-- 
Cheers.

Mark Lawrence.