v2ex-559776-answer.py

def real_to_hex(x, k=16):
    assert(0 <= x < 1)
    s = ['0.']
    for i in range(k):
        y = int(x * 16)
        s.append(hex(y)[2:])
        x = x * 16 - y
    return ''.join(s).rstrip('0')

Thanks