Binary Decimals in Python

[Mensanator]

On Mar 30, 10:49 am, Raymond Hettinger <pyt... at rcn.com> wrote:
> On Mar 30, 8:13 am, aditya <bluemangrou... at gmail.com> wrote:
>
> > To get the decimal representation of a binary number, I can just do
> > this:
>
> > int('11',2) # returns 3
>
> > But decimal binary numbers throw a ValueError:
>
> > int('1.1',2) # should return 1.5, throws error instead.
>
> > Is this by design? It seems to me that this is not the correct
> > behavior.
>
> The int() constructor returns integers.
> So, look to float() for non-integral values.
> Binary representation isn't supported yet,

It is supported in the gmpy module.

>>> import gmpy
>>> help(gmpy.mpf)
Help on built-in function mpf in module gmpy:

mpf(...)
    mpf(n): builds an mpf object with a numeric value n (n may be any
            Python number, or an mpz, mpq, or mpf object) and a
default
            precision (in bits) depending on the nature of n
    mpf(n,bits=0): as above, but with the specified number of bits (0
            means to use default precision, as above)
    mpf(s,bits=0,base=10): builds an mpf object from a string s made
up of
            digits in the given base, possibly with fraction-part
(with
            period as a separator) and/or exponent-part (with exponent
            marker 'e' for base<=10, else '@'). If base=256, s must be
            a gmpy.mpf portable binary representation as built by the
            function gmpy.fbinary (and the .binary method of mpf
objects).
            The resulting mpf object is built with a default precision
(in
            bits) if bits is 0 or absent, else with the specified
number
            of bits.

>>> gmpy.mpf('1.1',0,2)
mpf('1.5e0')


> but we do have hex:
>
>     >>> float.fromhex('1.8')
>     1.5
>
> Raymond