integer to binary...

Claudio Grondi claudio.grondi at freenet.de
Fri Jun 2 16:08:25 CEST 2006


mensanator at aol.com wrote:
> nicolasg at gmail.com wrote:
> 
>>does anyone know a module or something to convert numbers like integer
>>to binary format ?
>>
>>for example I want to convert number 7 to 0111 so I can make some
>>bitwise operations...
>>
>>Thanks
> 
> 
> Use the gmpy module.
> 
> 
>>>>import gmpy
>>>>a = 14
>>>>b = 7
>>>>c = 8
> 
> 
>>>>help(gmpy.digits)
> 
> Help on built-in function digits:
> 
> digits(...)
>     digits(x[,base]): returns Python string representing x in the
>     given base (2 to 36, default 10 if omitted or 0); leading '-'
>     present if x<0, but no leading '+' if x>=0. x must be an mpz,
>     or else gets coerced into one.
> 
> 
>>>>print gmpy.digits(a,2)
> 
> 1110
> 
>>>>print gmpy.digits(b,2)
> 
> 111
> 
>>>>print gmpy.digits(c,2)
> 
> 1000
> 
> 
> 
>>>>help(gmpy.setbit)
> 
> Help on built-in function setbit:
> 
> setbit(...)
>     setbit(x,n,v=1): returns a copy of the value of x, with bit n set
>     to value v; n must be an ordinary Python int, >=0; v, 0 or !=0;
>     x must be an mpz, or else gets coerced to one.
> 
> 
>>>>d = gmpy.setbit(c,1,1)
>>>>print gmpy.digits(d,2)
> 
> 1010
> 
> 
> 
> 
>>>>help(gmpy.scan1)
> 
> Help on built-in function scan1:
> 
> scan1(...)
>     scan1(x, n=0): returns the bit-index of the first 1-bit of x (that
>     is at least n); n must be an ordinary Python int, >=0.  If no more
>     1-bits are in x at or above bit-index n (which can only happen for
>     x>=0, notionally extended with infinite 0-bits), None is returned.
>     x must be an mpz, or else gets coerced to one.
> 
> 
>>>>help(gmpy.scan0)
> 
> Help on built-in function scan0:
> 
> scan0(...)
>     scan0(x, n=0): returns the bit-index of the first 0-bit of x (that
>     is at least n); n must be an ordinary Python int, >=0.  If no more
>     0-bits are in x at or above bit-index n (which can only happen for
>     x<0, notionally extended with infinite 1-bits), None is returned.
>     x must be an mpz, or else gets coerced to one.
> 
> 
>>>>print gmpy.scan1(a)
> 
> 1
> 
>>>>print gmpy.scan1(b)
> 
> 0
> 
>>>>print gmpy.scan1(c)
> 
> 3
> 
>>>>print gmpy.scan1(d)
> 
> 1
> 
>>>>print gmpy.scan0(a)
> 
> 0
> 
>>>>print gmpy.scan0(b)
> 
> 3
> 
>>>>print gmpy.scan0(c)
> 
> 0
> 
>>>>print gmpy.scan0(d)
> 
> 0
> 
> 
>>>>help(gmpy.popcount)
> 
> Help on built-in function popcount:
> 
> popcount(...)
>     popcount(x): returns the number of 1-bits set in x; note that
>     this is 'infinite' if x<0, and in that case, -1 is returned.
>     x must be an mpz, or else gets coerced to one.
> 
> 
>>>>print gmpy.popcount(a)
> 
> 3
> 
>>>>print gmpy.popcount(b)
> 
> 3
> 
>>>>print gmpy.popcount(c)
> 
> 1
> 
>>>>print gmpy.popcount(d)
> 
> 2
> 
> 
> 
>>>>help(gmpy.hamdist)
> 
> Help on built-in function hamdist:
> 
> hamdist(...)
>     hamdist(x,y): returns the Hamming distance (number of bit-positions
>     where the bits differ) between x and y.  x and y must be mpz, or
> else
>     get coerced to mpz.
> 
> 
>>>>print gmpy.hamdist(a,b)
> 
> 2
> 
>>>>print gmpy.hamdist(a,c)
> 
> 2
> 
>>>>print gmpy.hamdist(a,d)
> 
> 1
> 
>>>>print gmpy.hamdist(b,c)
> 
> 4
> 
>>>>print gmpy.hamdist(b,d)
> 
> 3
> 
>>>>print gmpy.hamdist(c,d)
> 
> 1
> 
For those digging deeper into this subject who are looking for speed, 
reading the past discussion on this newsgroup I was part of myself 
looking for fastest way of such integer to binary conversion can maybe 
be of interest:
   http://mail.python.org/pipermail/python-list/2006-January/319295.html
(includes full source code of all compared approaches)

Claudio



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