def is_number(arg: str):
    """
        string is number like 1.0, -1
            >>> is_number('1.5')
    """
    if len(arg) > 1 and arg[0] == '0':
        return False
    if arg.startswith('-'):
        arg = arg[1:]
    if arg.isdigit():
        return True
    if arg.find('.') > 0:
        args = arg.split('.')
        if len(args) > 0:
            if args[0].isdigit() and args[1].isdigit():
                return True
    return False