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

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> From: steve+comp.lang.python@pearwood.info
> Subject: Re: How to get an integer from a sequence of bytes
> Date: Mon, 27 May 2013 15:00:39 +0000
> To: python-list@python.org
>
> On Mon, 27 May 2013 16:45:05 +0200, 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?
>
> Here's one way:
>
> py> n = 11999102937234
> py> m = 0
> py> for b in n.to_bytes(6, 'big'):
> ... m = 256*m + b
> ...
> py> m == n
> True
>
>
> --
> Steven
>
> --
> http://mail.python.org/mailman/listinfo/python-list

Python 2 doesn't have to_bytes()! :(

# Python 2, LSB 1st
def to_lil_bytes(x):
    r = []
    while x != 0:
        r.append(int(x & 0b11111111))
        x>>= 8
    return r

# Python 2, LSB 1st
def from_lil_bytes(l):
    x = 0
    for i in range(len(l)-1, -1, -1):
        x <<= 8
        x |= l[i]
    return x

# Python 2, MSB 1st
def to_big_bytes(x):
    r = []
    while x != 0:
        r.insert(0, int(x & 0b11111111))
        x>>= 8
    return r

# Python 2, MSB 1st
def from_big_bytes(l):
    x = 0
    for i in range(len(l)):
        x <<= 8
        x |= l[i]
    return x

Can it be faster? 		 	   		  

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Thread

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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