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

[Prasad, Ramit]

> 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.

[ snip program ]

> data = bin(int(binascii.hexlify(bytes(data, 'UTF-8')), 16))
> data = binascii.unhexlify('%x' % data)

[ more snipping ]

> wolfrage at lm12-laptop02 ~/Projects $ python3 test_script.py
> Bit Length: 134
> 0b10101000110010101110011011101000110100101101110011001110010000001011000010011110101001000100000010000010110011101100001011010010110111000100001
> 7351954002991226380810260999848996570230305
> Traceback (most recent call last):
> File "test_script.py", line 24, in <module>
> data = binascii.unhexlify('%x' % data)
> TypeError: 'str' does not support the buffer interface

I think your basic problem is too much conversion because you do not
understand the types. A string is represented by a series of bytes
which are binary numbers. Do you understand the concept behind ASCII?
Each letter has a numeric representation that are sequential.
So the string 'abcd' is equivalent to a series of bytes 65,66,67,68.
It is not equivalent to 65666768 or 65+66+67+68. So your first
task is to convert each character to the numeric equivalent and store
them in a list. Once you have them converted to a list of integers,
you can create another list that is a list of characters.

Look at the functions chr and ord here
( http://docs.python.org/py3k/library/functions.html )

Ramit


Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology
712 Main Street | Houston, TX 77002
work phone: 713 - 216 - 5423

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