def zipnumber(a,b):
    """
    >>> zipnumber("1.2","345")
    [['0','3'],['0','4'],['1','5'],['.','.'],['2','0']]
    """
    if '.' in a or '.' in b:
        app = a.find('.')
        if app == -1:
            a += '.'
            app == len(a)
        bpp = b.find('.')
        if bpp == -1:
            b += '.'
            bpp == len(b)
        while app != bpp:
            if app < bpp:
                a += '0'
                app += 1
            else:
                b += '0'
                bpp += 1
    al = len(a)
    bl = len(b)
    if al > bl:
        b.ljust(al-bl,'0')
    elif al < bl:
        a.ljust(bl-al,'0')
    return zip(a,b)

def add(a,b):
    """
    >>> add("123","432")
    '555'
    >>> add("1.2","34")
    '35.2'
    """
    c = ""
    for aa,bb in zip(a,b):
        if aa != '.' and bb != '.':
            c += str(int(aa) + int(bb))
    return c

def sub(a,b):
    raise "TODO"

def mul(a,b):
    raise "TODO"


if __name__ == "__main__":
    import doctest
    doctest.testmod()