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Mon Apr 23 09:31:01 EDT 2001 · http://mail.python.org/pipermail/python-list/2001-April/078978.html

I needed to convert integers to binary representation and couldn't
find a builtin function. So here's what I came up with. The idea is to
return a string as short as possible and have positive numbers always
start with a  "0".

I wonder if there's a better way? 

And most probably there are lots of modules around offering  a
solution, aren't they?

Martin Bless

b_nibbles = [
    '0000', '0001', '0010', '0011',
    '0100', '0101', '0110', '0111',
    '1000', '1001', '1010', '1011',
    '1100', '1101', '1110', '1111']

# Another way to create b_nibbles:
#   b_nibbles = [a+b+c+d for a in ['0','1'] for b in ['0','1'] \
#                        for c in ['0','1'] for d in ['0','1']]

def i2bstr(arg):
    """Return integer as binary string."""
    import sys
    isPositive = (arg >= 0)
    maskHighNibble = sys.maxint >> 3
    r = ''
    while 1:
        r = b_nibbles[arg & 0xF] + r
        arg = (arg >> 4) & maskHighNibble
        if not arg:
            if isPositive and r[0] == '1':
                return '0000' + r
            else:
                return r

def test_i2bstr():
    """Demonstration of i2bstr()."""
    import sys
    integers = [0,1,15,16,255,256,32767,32768,
                sys.maxint,-sys.maxint-1,-256,-32768, -1]
    for i in integers:
        print "%12d %s" % (i, i2bstr(i))

## Output:
##           0 0000
##           1 0001
##          15 00001111
##          16 00010000
##         255 000011111111
##         256 000100000000
##       32767 0111111111111111
##       32768 00001000000000000000
##  2147483647 01111111111111111111111111111111
## -2147483648 10000000000000000000000000000000
##        -256 11111111111111111111111100000000
##      -32768 11111111111111111000000000000000
##          -1 11111111111111111111111111111111

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int 2 binary: What do you think?