def parrot(voltage, state='a stiff', action='voom', parrot_type='Norwegian Blue'):
    """多参数函数的示例

    这个函数接受一个必选参数(voltage)和三个可选参数
    (state, action, and type).
    """

    message = 'This parrot wouldn\'t ' + action + ' '
    message += 'if you put ' + str(voltage) + ' volts through it. '
    message += 'Lovely plumage, the ' + parrot_type + '. '
    message += 'It\'s ' + state + '!'

    return message