python速成课程：第9章-创建一个class_dog示例答案

【问题标题】：python crash course: ch 9- creating a class_ dog examplepython速成课程：第9章-创建一个class_dog示例
【发布时间】：2018-10-28 17:31:06
【问题描述】：

您好，我无法弄清楚我在以下代码中做错了什么以产生错误消息，我已经从网络上复制并粘贴了相同的代码，它工作得很好，但是当我输入它时定义的类似乎没有参数。

输入：

class Dog():
  """A simple attempt to model a dog"""
  def _init_(self, name, age):
    """initialize name and age attributes."""
    self.name = name
    self.age = age

  def sit(self):
    """simulate dog sitting in response to a command"""
    print(self.name.title() + " is now sitting.")

  def roll_over(self):
    """simulate rolling over in response to a command"""
    print(self.name.title() + " rolled over!")

my_dog = Dog('willie', 6)
print("My dog's name is " + my_dog.name.title() + ".")
print("My dog is " + str(my_dog.age) + " years old.")

输出：

 Traceback (most recent call last):
  File "C:/Users/sstie/Desktop/python_work/ch.9_retry.py", line 16, in <module>
    my_dog = Dog('willie', 6)
TypeError: Dog() takes no arguments

【问题讨论】：

_init_ 需要两个下划线。
你的缩进是错误的。

标签： python python-3.x class instance

【解决方案1】：

您的构造函数名称中需要两个下划线：

class Dog:
    """A simple attempt to model a dog"""
    def __init__(self, name, age):
        """initialize name and age attributes."""
        self.name = name
        self.age = age

    def sit(self):
        """simulate dog sitting in response to a command"""
        print(self.name.title() + " is now sitting.")

    def roll_over(self):
        """simulate rolling over in response to a command"""
        print(self.name.title() + " rolled over!")

my_dog = Dog('willie', 6)
print("My dog's name is " + my_dog.name.title() + ".")
print("My dog is " + str(my_dog.age) + " years old.")

python 中的许多special names 以双下划线开头和结尾。

【讨论】：