Object-oriented: Python simple class encapsulation case exercise

01. Packaging

1. Encapsulation is a major feature of object-oriented programming
2. Object-oriented programming in the first step - the attributes and methods packaged into an abstract class in
3. The outside world using a class to create an object , and then let the object calls methods
4. Details of the method of the object are encapsulated in the interior of the class

02. Case 1_Xiao Mingai running

demand

1. Xiaoming's weight 75.0 kg
2. Xiao Ming each runner will lose weight 0.5kilo
3. Xiao Ming each eating weight gain 1kg

Tip: In -house method object , it can attribute directly access the object 's!

• Code:

class Person:
    """人类"""

    def __init__(self, name, weight):

        self.name = name
        self.weight = weight

    def __str__(self):

        return "我的名字叫 %s 体重 %.2f 公斤" % (self.name, self.weight)

    def run(self):
        """跑步"""

        print("%s 爱跑步，跑步锻炼身体" % self.name)
        self.weight -= 0.5

    def eat(self):
        """吃东西"""

        print("%s 是吃货，吃完这顿再减肥" % self.name)
        self.weight += 1


xiaoming = Person("小明", 75)

xiaoming.run()
xiaoming.eat()
xiaoming.eat()

print(xiaoming)

03. Case 2_ Place furniture

demand

1. House (House) have units , the total area and furniture name list
   • The new house has no furniture
2. Furniture (HouseItem) have names and covers an area where
   • Simmons (bed) covers an area of 4square meters
   • Wardrobe (chest) area 2square meter
   • Table (table) area 1.5m²
3. The above three furniture added to the house in
4. When printing a house, it is required to output: house type , total area , remaining area , list of furniture names

Remaining area

1. When creating the house object is defined a property of the remaining area , the initial value is equal to the total area, and
2. When you call the add_itemmethod, to the room to add furniture , the let the remaining area - = furniture area

3.1 Create furniture

class HouseItem:

    def __init__(self, name, area):
        """

        :param name: 家具名称
        :param area: 占地面积
        """
        self.name = name
        self.area = area

    def __str__(self):
        return "[%s] 占地面积 %.2f" % (self.name, self.area)


# 1. 创建家具
bed = HouseItem("席梦思", 4)
chest = HouseItem("衣柜", 2)
table = HouseItem("餐桌", 1.5)

print(bed)
print(chest)
print(table)

summary

1. Created a furniture , to use __init__and __str__two built-in method
2. Use furniture to create three furniture objects , and output information Furniture

3.2 Create a room

class House:

    def __init__(self, house_type, area):
        """

        :param house_type: 户型
        :param area: 总面积
        """
        self.house_type = house_type
        self.area = area
        
        # 剩余面积默认和总面积一致
        self.free_area = area
        # 默认没有任何的家具
        self.item_list = []

    def __str__(self):

        # Python 能够自动的将一对括号内部的代码连接在一起
        return ("户型：%s\n总面积：%.2f[剩余：%.2f]\n家具：%s"
                % (self.house_type, self.area,
                   self.free_area, self.item_list))

    def add_item(self, item):

        print("要添加 %s" % item)

...

# 2. 创建房子对象
my_home = House("两室一厅", 60)

my_home.add_item(bed)
my_home.add_item(chest)
my_home.add_item(table)

print(my_home)

summary

1. Creating a house class , to use __init__and __str__two built-in method
2. Preparing a add_itemmethod ready to add furniture
3. Use house class created a house Object
4. Let the house objects called three times add_itemmethod, the three furniture to arguments passed to the add_iteminterior

3.3 Add furniture

demand

• 1> Analyzing furniture area whether or exceeds the remaining area , if exceeded , can not be prompted to add the piece of furniture
• 2> The name of the furniture added to the furniture list of names of
• 3> with the remaining area of the house - furniture area

    def add_item(self, item):

        print("要添加 %s" % item)
        # 1. 判断家具面积是否大于剩余面积
        if item.area > self.free_area:
            print("%s 的面积太大，不能添加到房子中" % item.name)

            return

        # 2. 将家具的名称追加到名称列表中
        self.item_list.append(item.name)

        # 3. 计算剩余面积
        self.free_area -= item.area

3.4 Summary

• The main program is only responsible for creating house objects and furniture objects
• Let the house object call add_itemmethod will be added to the house furniture in
• Area calculations , the remaining area , furniture list and other processing are encapsulated into the interior of the house class

04. Case 3_ Soldier Assault

demand

1. Soldier Xu Sanduo has an AK47
2. Soldiers can fire
3. Gun capable of launching a bullet
4. Gun loading loading bullets - to increase the number of bullets

4.1 Development of guns

shoot Method requirements

• 1> Judge whether there are bullets, you can’t shoot without bullets
• 2> use printtips the shooting, and outputs the number of bullets

class Gun:

    def __init__(self, model):

        # 枪的型号
        self.model = model
        # 子弹数量
        self.bullet_count = 0

    def add_bullet(self, count):

        self.bullet_count += count

    def shoot(self):

        # 判断是否还有子弹
        if self.bullet_count <= 0:
            print("没有子弹了...")

            return

        # 发射一颗子弹
        self.bullet_count -= 1
        
        print("%s 发射子弹[%d]..." % (self.model, self.bullet_count))

# 创建枪对象
ak47 = Gun("ak47")
ak47.add_bullet(50)
ak47.shoot()

4.2 Develop Soldiers

Assumptions: Every recruits have no guns

Define an attribute with no initial value

When defining attributes, if anything does not know the initial value setting , it can be set toNone

• None Keyword represents nothing
• Denotes a null object , no methods and properties, is a special constant
• You can be Noneassigned to any variable

fire Method requirements

• 1> Determine whether there is a gun, you can’t charge without a gun
• 2> Shout a slogan
• 3> Loading bullets
• 4> Shooting

class Soldier:

    def __init__(self, name):

        # 姓名
        self.name = name
        # 枪，士兵初始没有枪 None 关键字表示什么都没有
        self.gun = None

    def fire(self):

        # 1. 判断士兵是否有枪
        if self.gun is None:
            print("[%s] 还没有枪..." % self.name)

            return

        # 2. 高喊口号
        print("冲啊...[%s]" % self.name)

        # 3. 让枪装填子弹
        self.gun.add_bullet(50)

        # 4. 让枪发射子弹
        self.gun.shoot()

summary

1. Creating a soldier class , use the __init__built-in method
2. When defining attributes, if anything does not know the initial value setting , it can be set toNone
3. In the package of internal methods, you can also make your own objects created using other classes of property calls have been packaged method

05. Identity Operator

Identity operator is used to compare two objects of memory addresses are the same - whether it is a reference to the same object

• In Pythonthe For Nonecomparison, it is recommended to use isjudgment

Operator	description	Instance
is	is is to judge whether two identifiers refer to the same object	x is y，类似 id(x) == id(y)
is not	is not is to judge whether two identifiers refer to different objects	x is not y，类似 id(a) != id(b)

The difference between is and ==:

isFor determining two variables refer to the same whether the object
== for determining the value of the reference variable is equal

>>> a = [1, 2, 3]
>>> b = [1, 2, 3]
>>> b is a 
False
>>> b == a
True