面向对象的特殊方法

Posted 2020-11-06

特殊方法

__init__ :把各种属性绑定到self

__slots__ : 限制实例的动态属性，减少内存消耗，tuple类型

__str__: 对象的说明文字

__eq__:比较对象是否相等

classmethod 与staticmethod:classmethod 会把类本身作为第一个参数传入。

class Computer:
    """电脑"""
    def __init__(self, name, mem, cpu):
        self._name = name 
        self.mem = mem
        self.cpu = cpu 

    def play(self, game=‘qq‘):
        print(‘play games:‘,game)

pc1 = Computer(‘coop‘,‘8G‘,‘8‘)  # 实例初始化，生成一个类的对象，具有类的属性和方法

pc1

<__main__.Computer at 0x1ec1ec7f0f0>

pc1.play

<bound method Computer.play of <__main__.Computer object at 0x000001EC1EC7F0F0>>

pc1.play()

play games: qq

pc1.play(‘rongyao‘)

play games: rongyao

pc1.mem

‘8G‘

pc1._name

‘coop‘

pc1.cpu

‘8‘

#############

pc1.disk = ‘ssd‘

pc1.disk

‘ssd‘

class Computer:
    """电脑"""
    __slots__ = (‘_name‘, ‘mem‘, ‘cpu‘)
    def __init__(self, name, mem, cpu):
        self._name = name 
        self.mem = mem
        self.cpu = cpu

    def play(self, game=‘mosou‘):
        print(‘play game:‘,game)

    def __str__(self):
        return f‘{self._name}:{self.mem}-{self.cpu}‘

pc2 = Computer(‘admin‘, ‘8G‘, ‘8‘)

pc2.mem

‘8G‘

pc2.cpu

‘8‘

pc2._name

‘admin‘

pc2.disk = ‘disk‘

---------------------------------------------------------------------------

AttributeError                            Traceback (most recent call last)

<ipython-input-45-35b41d1e04d2> in <module>()
----> 1 pc2.disk = ‘disk‘

AttributeError: ‘Computer‘ object has no attribute ‘disk‘

print(pc2)

admin:8G-8

pc3 = Computer(‘admin‘,‘8G‘,8)

print(pc3)

admin:8G-8

pc2 == pc3

False

############

class Computer:
    """电脑"""
    __slots__ = (‘_name‘, ‘mem‘, ‘cpu‘)
    def __init__(self, name, mem, cpu):
        self._name = name 
        self.mem = mem
        self.cpu = cpu

    def play(self, game=‘mosou‘):
        print(‘play game:‘,game)

    def __str__(self):
        return f‘{self._name}:{self.mem}-{self.cpu}‘

    def __eq__(self, other):
        return self.cpu == other.cpu

pc2 = Computer(‘admin‘,‘8G‘,8)

pc3 = Computer(‘admin‘,‘8G‘,8)

pc2 == pc3

True

###########

class Computer:
    """电脑"""
    __slots__ = (‘_name‘, ‘mem‘, ‘cpu‘)
    def __init__(self, name, mem, cpu):
        self._name = name 
        self.mem = mem
        self.cpu = cpu

    def play(self, game=‘mosou‘):
        print(‘play game:‘,game)

    def __str__(self):
        return f‘{self._name}:{self.mem}-{self.cpu}‘

    def __eq__(self, other):
        return self.cpu == other.cpu

    @classmethod  # 通过新的方式构造实例，区别于默认的__init__,类似其他语言重载
    def new_pc(cls, info):  # 第一个参数为类本身
        "从字符串产生新的实例"
        name, mem, cpu = info.split(‘-‘)
        return cls(name, mem, cpu)

    @staticmethod  # 不需要生成类的实例，就可以使用的方法
    def calc(a, b, oper):  # 不用第一个参数
        "根据操作符号+-*/计算a和b的结果"
        if oper == ‘+‘:
            return a + b

# 使用classmethod建立新的对象
pc111 = Computer.new_pc(‘pc111-16G-8‘)

print(pc111)

pc111:16G-8

Computer.calc(4, 3, ‘+‘)

7

Computer.calc(2, 3, "-")