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Re: How to get an integer from a sequence of bytes

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Am 30.05.2013 21:22, schrieb Ned Batchelder:
>
> On 5/30/2013 2:26 PM, Mok-Kong Shen wrote:
>> Am 27.05.2013 17:30, schrieb Ned Batchelder:
>>> On 5/27/2013 10:45 AM, Mok-Kong Shen wrote:
>>>> From an int one can use to_bytes to get its individual bytes,
>>>> but how can one reconstruct the int from the sequence of bytes?
>>>>
>>> The next thing in the docs after int.to_bytes is int.from_bytes:
>>> http://docs.python.org/3.3/library/stdtypes.html#int.from_bytes
>>
>> I am sorry to have overlooked that. But one thing I yet wonder is why
>> there is no direct possibilty of converting a byte to an int in [0,255],
>> i.e. with a constrct int(b), where b is a byte.
>>
>
> Presumably you want this to work:
>
>      >>> int(b'\x03')
>      3
>
> But you also want this to work:
>
>      >>> int(b'7')
>      7
>
> These two interpretations are incompatible.  If b'\x03' becomes 3, then
> shouldn't b'\x37' become 55?  But b'\x37' is b'7', and you want that to
> be 7.

b'7' is the byte with the character 7 in a certain code, so that's
ok. In other PLs one assigns an int to a byte, with that int in either
decimal notation or hexadecimal notation, or else one assigns a
character to it, in which case it gets the value of the character
in a certain code. What I don't yet understand is why Python is
apprently different from other PLs in that point in not allowing direct
coersion of a byte to an int.

M. K. Shen

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How to get an integer from a sequence of bytes Mok-Kong Shen <mok-kong.shen@t-online.de> - 2013-05-27 16:45 +0200
  Re: How to get an integer from a sequence of bytes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-05-27 15:00 +0000
    RE: How to get an integer from a sequence of bytes Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-05-28 03:37 +0300
  Re: How to get an integer from a sequence of bytes Ned Batchelder <ned@nedbatchelder.com> - 2013-05-27 11:30 -0400
    Re: How to get an integer from a sequence of bytes Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-05-28 00:31 +0000
      Re: How to get an integer from a sequence of bytes Dave Angel <davea@davea.name> - 2013-05-27 20:41 -0400
    Re: How to get an integer from a sequence of bytes Mok-Kong Shen <mok-kong.shen@t-online.de> - 2013-05-30 20:26 +0200
      Re: How to get an integer from a sequence of bytes Ian Kelly <ian.g.kelly@gmail.com> - 2013-05-30 12:42 -0600
        Re: How to get an integer from a sequence of bytes jmfauth <wxjmfauth@gmail.com> - 2013-05-30 11:53 -0700
      Re: How to get an integer from a sequence of bytes Ned Batchelder <ned@nedbatchelder.com> - 2013-05-30 15:22 -0400
        Re: How to get an integer from a sequence of bytes Mok-Kong Shen <mok-kong.shen@t-online.de> - 2013-06-02 21:25 +0200
          Re: How to get an integer from a sequence of bytes Chris Angelico <rosuav@gmail.com> - 2013-06-03 05:54 +1000
          Re: How to get an integer from a sequence of bytes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-02 21:48 -0400
            Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-06-03 14:31 +0000
              Re: How to get an integer from a sequence of bytes Dave Angel <d@davea.name> - 2013-06-03 18:07 -0400
                Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-06-03 22:34 +0000
              Re: How to get an integer from a sequence of bytes Dan Stromberg <drsalists@gmail.com> - 2013-06-03 15:41 -0700
                Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-06-04 13:39 +0000
                Re: How to get an integer from a sequence of bytes Joshua Landau <joshua.landau.ws@gmail.com> - 2013-06-04 20:51 +0100
                Re: How to get an integer from a sequence of bytes Chris Angelico <rosuav@gmail.com> - 2013-06-05 07:49 +1000
                Re: How to get an integer from a sequence of bytes Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-04 20:34 -0400
                Re: How to get an integer from a sequence of bytes Tim Roberts <timr@probo.com> - 2013-06-04 22:11 -0700
                Re: How to get an integer from a sequence of bytes Fábio Santos <fabiosantosart@gmail.com> - 2013-06-12 15:00 +0100
                Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-06-12 14:42 +0000
              RE: How to get an integer from a sequence of bytes Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-06-04 02:18 +0300
                Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-06-04 13:42 +0000
                RE: How to get an integer from a sequence of bytes Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-06-04 16:58 +0300
              Re: How to get an integer from a sequence of bytes Dan Stromberg <drsalists@gmail.com> - 2013-06-03 16:47 -0700
  Re: How to get an integer from a sequence of bytes Grant Edwards <invalid@invalid.invalid> - 2013-05-28 16:04 +0000

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