day 21 作业

定义MySQL类

• 对象有id、host、port三个属性
• 定义工具create_id，在实例化时为每个对象随机生成id，保证id唯一
• 提供两种实例化方式，方式一：用户传入host和port 方式二：从配置文件中读取host和port进行实例化
• 为对象定制方法，save和get_obj_by_id，save能自动将对象序列化到文件中，文件路径为配置文件中 DB_PATH,文件名为id号，保存之前验证对象是否已经存在，若存在则抛出异常,get_obj_by_id方法用来从文件中反序列化出对象

Copyfrom conf import settings
import uuid
import pickle
import os

class MySQL:
    def __init__(self, host, port):
        self.id = self.create_id()
        self.host = host
        self.port = port

    def save(self):
        if self.is_exists:
            raise PermissionError('对象已存在')
        file_path = f'{settings.DB_PATH}{os.sep}{self.id}'
        pickle.dump(self, open(file_path, 'wb'))

    @property
    def is_exists(self):
        tag = False
        files = os.listdir(settings.DB_PATH)

        for file in files:
            file_abspath = f'{settings.DB_PATH}{os.sep}{file}'
            obj = pickle.load(open(file_abspath, 'rb'))
            if self.host == obj.host and self.port == obj.port:
                tag = True
                break

        return tag

    @staticmethod
    def get_obj_by_id(id):
        file_path = f'{settings.DB_PATH}{os.sep}{id}'
        return pickle.load(open(file_path, 'rb'))

    @staticmethod
    def create_id():
        return str(uuid.uuid1())

    @classmethod
    def from_conf(cls):
        print(cls)
        return cls(settings.HOST, settings.PORT)

# conn = MySQL.from_conf()
# conn.save()

obj = MySQL.get_obj_by_id('504ab0f6-ec21-11e9-b9e2-d053497faa26')
print(obj.host)

定义一个类：圆形，该类有半径，周长，面积等属性，将半径隐藏起来，将周长与面积开放

Copyfrom math import pi

class Round:
    def __init__(self, radius):
        self.__radius = radius

    def perimeter(self):
        return round(2 * pi * self.__radius, 2)

    def area(self):
        return round(pi * (self.__radius ** 2), 2)

r = Round(1)
print(r.area())
print(r.perimeter())
print(r._Round__radius)

使用abc模块定义一个phone抽象类 并编写一个具体的实现类

Copyimport abc

# 抽象类/父类
class CellPhone(metaclass=abc.ABCMeta):

    @abc.abstractmethod
    def calling(self):
        pass

    @abc.abstractmethod
    def send_msg(self):
        pass

# 现实类/子类
class SmartPhone(CellPhone):

    def calling(self):
        print('calling...')

    # def send_msg(self):
    #     print('sending msg...')

    def app_download(self):
        print('downloading app...')

iphone = SmartPhone()
iphone.calling()
iphone.send_msg()
iphone.app_download()