Reading a binary file

[Andrew Bennetts]

On Thu, Jun 26, 2003 at 11:33:20AM +0200, Sorin Marti wrote:
> Andrew Bennetts wrote:
> >On Thu, Jun 26, 2003 at 10:01:06AM +0200, Sorin Marti wrote:
> >
> >>But now I need the hex values of the binary file.
> >
> >You can get the hex value of a 1-character string with hex(ord(char)), 
> >e.g.:
> >
> >    >>> char = 'a'
> >    >>> hex(ord(char))
> >    '0x61'
> >
> 
> That is not exactly what I meant. I've found a solution (a is the binary 
> data):
> 
> b = binascii.hexlify(a)
> 
> For example it gives me C8 which is a HEX-Value. How to change this one 
> into a decimal? (The decimal should be 130, right?)

I think you might be confused about how bytes and numbers are related.  Have
a look at this:

    >>> char = 'a'
    >>> ord(char)
    97
    >>> type(ord(char))
    <type 'int'>
    >>> type(hex(ord(char)))
    <type 'str'>

So I'm guessing you don't really want the hex representation at all!

A quick way to convert a string of bytes into the corresponding numerical
values is:

    >>> s = 'hello'
    >>> map(ord, s)
    [104, 101, 108, 108, 111]

or:

    >>> s = 'hello'
    >>> [ord(char) for char in s]
    [104, 101, 108, 108, 111]

And again, I *strongly* suggest you look at the struct module -- I'm not
sure what you're trying to do, but if you're trying to interpret binary data
into numbers and things, it's almost certainly helpful:

    http://python.org/doc/current/lib/module-struct.html

e.g.:

    >>> s = 'hello'
    >>> struct.unpack('5B', s)
    (104, 101, 108, 108, 111)

-Andrew.