设计模式python总结

代码: https://github.com/youngsterxyf/mpdp-code

创建型

1. 工厂模式

场景:
客户端1可以请求一个对象，而无需知道这个对象来自哪里
创建对象的代码和使用对象的代码解耦
我们执行单个函数，传入一个参数(提供信息表明我们想要什么)，但
并不要求知道任何关于对象如何实现以及对象来自哪里的细节。

import xml.etree.ElementTree as etree
import json


class JSONConnector:

    def __init__(self, filepath):
        self.data = dict()
        with open(filepath, mode='r', encoding='utf-8') as f:
            self.data = json.load(f)

    @property
    def parsed_data(self):
        return self.data


class XMLConnector:

    def __init__(self, filepath):
        self.tree = etree.parse(filepath)

    @property
    def parsed_data(self):
        return self.tree


def connection_factory(filepath):
    if filepath.endswith('json'):
        connector = JSONConnector
    elif filepath.endswith('xml'):
        connector = XMLConnector
    else:
        raise ValueError('Cannot connect to {}'.format(filepath))
    return connector(filepath)


def connect_to(filepath):
    factory = None
    try:
        factory = connection_factory(filepath)
    except ValueError as ve:
        print(ve)
    return factory


def main():
    sqlite_factory = connect_to('data/person.sq3')
    print()

    xml_factory = connect_to('data/person.xml')
    xml_data = xml_factory.parsed_data
    liars = xml_data.findall(".//{}[{}='{}']".format('person',
                                                     'lastName', 'Liar'))
    print('found: {} persons'.format(len(liars)))
    for liar in liars:
        print('first name: {}'.format(liar.find('firstName').text))
        print('last name: {}'.format(liar.find('lastName').text))
        [print('phone number ({})'.format(p.attrib['type']),
               p.text) for p in liar.find('phoneNumbers')]

    print()

    json_factory = connect_to('data/donut.json')
    json_data = json_factory.parsed_data
    print('found: {} donuts'.format(len(json_data)))
    for donut in json_data:
        print('name: {}'.format(donut['name']))
        print('price: ${}'.format(donut['ppu']))
        [print('topping: {} {}'.format(t['id'], t['type'])) for t in donut['topping']]

if __name__ == '__main__':
    main()

class Frog:

    def __init__(self, name):
        self.name = name

    def __str__(self):
        return self.name

    def interact_with(self, obstacle):
        print('{} the Frog encounters {} and {}!'.format(self,
                                                         obstacle, obstacle.action()))


class Bug:

    def __str__(self):
        return 'a bug'

    def action(self):
        return 'eats it'


class FrogWorld:

    def __init__(self, name):
        print(self)
        self.player_name = name

    def __str__(self):
        return '\n\n\t------ Frog World ———'

    def make_character(self):
        return Frog(self.player_name)

    def make_obstacle(self):
        return Bug()


class Wizard:

    def __init__(self, name):
        self.name = name

    def __str__(self):
        return self.name

    def interact_with(self, obstacle):
        print('{} the Wizard battles against {} and {}!'.format(self, obstacle, obstacle.action()))


class Ork:

    def __str__(self):
        return 'an evil ork'

    def action(self):
        return 'kills it'


class WizardWorld:

    def __init__(self, name):
        print(self)
        self.player_name = name

    def __str__(self):
        return '\n\n\t------ Wizard World ———'

    def make_character(self):
        return Wizard(self.player_name)

    def make_obstacle(self):
        return Ork()


class GameEnvironment:

    def __init__(self, factory):
        self.hero = factory.make_character()
        self.obstacle = factory.make_obstacle()

    def play(self):
        self.hero.interact_with(self.obstacle)


def validate_age(name):
    try:
        age = input('Welcome {}. How old are you? '.format(name))
        age = int(age)
    except ValueError as err:
        print("Age {} is invalid, please try \
        again…".format(age))
        return (False, age)
    return (True, age)


def main():
    name = input("Hello. What's your name? ")
    valid_input = False
    while not valid_input:
        valid_input, age = validate_age(name)
    game = FrogWorld if age < 18 else WizardWorld
    environment = GameEnvironment(game(name))
    environment.play()

if __name__ == '__main__':
    main()

2. 建造者模式

场景:
即使存在多种汉堡包(经典款、奶酪汉堡包等)和不同 包装(小盒子、中等大小盒子等)，准备一个汉堡包及打包(盒子或纸袋)的流程都是相同的
指挥者和建造者分开
Engineer 和 Builder 分开

# coding: utf-8
class Computer:

    def __init__(self, serial_number):
        self.serial = serial_number
        self.memory = None      # 单位为GB
        self.hdd = None         # 单位为GB
        self.gpu = None

    def __str__(self):
        info = ('Memory: {}GB'.format(self.memory),
                'Hard Disk: {}GB'.format(self.hdd),
                'Graphics Card: {}'.format(self.gpu))
        return '\n'.join(info)


class ComputerBuilder:

    def __init__(self):
        self.computer = Computer('AG23385193')

    def configure_memory(self, amount):
        self.computer.memory = amount

    def configure_hdd(self, amount):
        self.computer.hdd = amount

    def configure_gpu(self, gpu_model):
        self.computer.gpu = gpu_model


class HardwareEngineer:

    def __init__(self):
        self.builder = None

    def construct_computer(self, memory, hdd, gpu):
        self.builder = ComputerBuilder()
        [step for step in (self.builder.configure_memory(memory),
                           self.builder.configure_hdd(hdd),
                           self.builder.configure_gpu(gpu))]

    @property
    def computer(self):
        return self.builder.computer


def main():
    engineer = HardwareEngineer()
    engineer.construct_computer(hdd=500, memory=8, gpu='GeForce GTX 650 Ti')
    computer = engineer.computer
    print(computer)

if __name__ == '__main__':
    main()

3.原型模式

结构型

1. 适配器模式

class Adapter:
    def __init__(self, obj, adapted_methods):
        self.obj = obj
        self.__dict__.update(adapted_methods)
    def __str__(self):
        return str(self.obj)
        
def main():
	objects = [Computer('Asus')]
	synth = Synthesizer('moog')
	objects.append(Adapter(synth, dict(execute=synth.play)))
	human = Human('Bob')
	objects.append(Adapter(human, dict(execute=human.speak))) 12
    for i in objects:
      print('{} {}'.format(str(i), i.execute()))

2.修饰器模式

# coding: utf-8

import functools


def memoize(fn):
    known = dict()

    @functools.wraps(fn)
    def memoizer(*args):
        if args not in known:
            known[args] = fn(*args)
        return known[args]

    return memoizer


@memoize
def nsum(n):
    '''返回前n个数字的和'''
    assert(n >= 0), 'n must be >= 0'
    return 0 if n == 0 else n + nsum(n-1)


@memoize
def fibonacci(n):
    '''返回斐波那契数列的第n个数'''
    assert(n >= 0), 'n must be >= 0'
    return n if n in (0, 1) else fibonacci(n-1) + fibonacci(n-2)

if __name__ == '__main__':
    from timeit import Timer
    measure = [{'exec': 'fibonacci(100)', 'import': 'fibonacci',
                'func': fibonacci}, {'exec': 'nsum(200)', 'import': 'nsum',
                                     'func': nsum}]
    for m in measure:
        t = Timer('{}'.format(m['exec']), 'from __main__ import \
            {}'.format(m['import']))
        print('name: {}, doc: {}, executing: {}, time: \
            {}'.format(m['func'].__name__, m['func'].__doc__,
                       m['exec'], t.timeit()))

3.外观模式

我们并不想把这种复杂性暴露给客户端。外观设计模式有助于隐藏 系统的内部复杂性，并通过一个简化的接口向客户端暴露必要的部分

# coding: utf-8

from enum import Enum
from abc import ABCMeta, abstractmethod

State = Enum('State', 'new running sleeping restart zombie')


class User:
    pass


class Process:
    pass


class File:
    pass


class Server(metaclass=ABCMeta):

    @abstractmethod
    def __init__(self):
        pass

    def __str__(self):
        return self.name

    @abstractmethod
    def boot(self):
        pass

    @abstractmethod
    def kill(self, restart=True):
        pass


class FileServer(Server):

    def __init__(self):
        '''初始化文件服务进程要求的操作'''
        self.name = 'FileServer'
        self.state = State.new

    def boot(self):
        print('booting the {}'.format(self))
        '''启动文件服务进程要求的操作'''
        self.state = State.running

    def kill(self, restart=True):
        print('Killing {}'.format(self))
        '''杀死文件服务进程要求的操作'''
        self.state = State.restart if restart else State.zombie

    def create_file(self, user, name, permissions):
        '''检查访问权限的有效性、用户权限，等等'''

        print("trying to create the file '{}' for user '{}' with permissions {}".format(name, user, permissions))


class ProcessServer(Server):

    def __init__(self):
        '''初始化进程服务进程要求的操作'''
        self.name = 'ProcessServer'
        self.state = State.new

    def boot(self):
        print('booting the {}'.format(self))
        '''启动进程服务进程要求的操作'''
        self.state = State.running

    def kill(self, restart=True):
        print('Killing {}'.format(self))
        '''杀死进程服务进程要求的操作'''
        self.state = State.restart if restart else State.zombie

    def create_process(self, user, name):
        '''检查用户权限、生成PID，等等'''

        print("trying to create the process '{}' for user '{}'".format(name, user))


class WindowServer:
    pass


class NetworkServer:
    pass


class OperatingSystem:

    '''外观'''

    def __init__(self):
        self.fs = FileServer()
        self.ps = ProcessServer()

    def start(self):
        [i.boot() for i in (self.fs, self.ps)]

    def create_file(self, user, name, permissions):
        return self.fs.create_file(user, name, permissions)

    def create_process(self, user, name):
        return self.ps.create_process(user, name)


def main():
    os = OperatingSystem()
    os.start()
    os.create_file('foo', 'hello', '-rw-r-r')
    os.create_process('bar', 'ls /tmp')

if __name__ == '__main__':
    main()

4. MVC模式

quotes = ('A man is not complete until he is married. Then he is finished.',
          'As I said before, I never repeat myself.',
          'Behind a successful man is an exhausted woman.',
          'Black holes really suck...', 'Facts are stubborn things.')


class QuoteModel:

    def get_quote(self, n):
        try:
            value = quotes[n]
        except IndexError as err:
            value = 'Not found!'
        return value


class QuoteTerminalView:

    def show(self, quote):
        print('And the quote is: "{}"'.format(quote))

    def error(self, msg):
        print('Error: {}'.format(msg))

    def select_quote(self):
        return input('Which quote number would you like to see?')


class QuoteTerminalController:

    def __init__(self):
        self.model = QuoteModel()
        self.view = QuoteTerminalView()

    def run(self):
        valid_input = False
        while not valid_input:
            n = self.view.select_quote()
            try:
                n = int(n)
            except ValueError as err:
                self.view.error("Incorrect index '{}'".format(n))
            else:
                valid_input = True
        quote = self.model.get_quote(n)
        self.view.show(quote)


def main():
    controller = QuoteTerminalController()
    while True:
        controller.run()

if __name__ == '__main__':
    main()

5. 代理模式

# coding: utf-8


class SensitiveInfo:

    def __init__(self):
        self.users = ['nick', 'tom', 'ben', 'mike']

    def read(self):
        print('There are {} users: {}'.format(len(self.users), ' '.join(self.users)))

    def add(self, user):
        self.users.append(user)
        print('Added user {}'.format(user))


class Info:

    '''SensitiveInfo的保护代理'''

    def __init__(self):
        self.protected = SensitiveInfo()
        self.secret = '0xdeadbeef'

    def read(self):
        self.protected.read()

    def add(self, user):
        sec = input('what is the secret? ')
        self.protected.add(user) if sec == self.secret else print("That's wrong!")


def main():
    info = Info()
    while True:
        print('1. read list |==| 2. add user |==| 3. quit')
        key = input('choose option: ')
        if key == '1':
            info.read()
        elif key == '2':
            name = input('choose username: ')
            info.add(name)
        elif key == '3':
            exit()
        else:
            print('unknown option: {}'.format(key))

if __name__ == '__main__':
    main()

行为型

1. 责任链

多个对象来处理单个请求

class Event:

    def __init__(self, name):
        self.name = name

    def __str__(self):
        return self.name


class Widget:

    def __init__(self, parent=None):
        self.parent = parent

    def handle(self, event):
        handler = 'handle_{}'.format(event)
        if hasattr(self, handler):
            method = getattr(self, handler)
            method(event)
        elif self.parent:
            self.parent.handle(event)
        elif hasattr(self, 'handle_default'):
            self.handle_default(event)


class MainWindow(Widget):

    def handle_close(self, event):
        print('MainWindow: {}'.format(event))

    def handle_default(self, event):
        print('MainWindow Default: {}'.format(event))


class SendDialog(Widget):

    def handle_paint(self, event):
        print('SendDialog: {}'.format(event))


class MsgText(Widget):

    def handle_down(self, event):
        print('MsgText: {}'.format(event))


def main():
    mw = MainWindow()
    sd = SendDialog(mw)
    msg = MsgText(sd)

    for e in ('down', 'paint', 'unhandled', 'close'):
        evt = Event(e)
        print('\nSending event -{}- to MainWindow'.format(evt))
        mw.handle(evt)
        print('Sending event -{}- to SendDialog'.format(evt))
        sd.handle(evt)
        print('Sending event -{}- to MsgText'.format(evt))
        msg.handle(evt)

if __name__ == '__main__':
    main()

2. 命令模式

class Invoker {  
    private Command command;  
    public void setCommand(Command command) {  
        this.command = command;  
    }  
    public void action(){  
        this.command.execute();  
    }  
}  
  
abstract class Command {  
    public abstract void execute();  
}  
  
class ConcreteCommand extends Command {  
    private Receiver receiver;  
    public ConcreteCommand(Receiver receiver){  
        this.receiver = receiver;  
    }  
    public void execute() {  
        this.receiver.doSomething();  
    }  
}  

class ConcreteCommand2 extends Command {  
    private Receiver receiver;  
    public ConcreteCommand(Receiver receiver){  
        this.receiver = receiver;  
    }  
    public void execute() {  
        this.receiver.doSomething();  
    }  
}  

  
class Receiver {  
    public void doSomething(){  
        System.out.println("接受者-业务逻辑处理");  
    }  
}  
  
public class Client {  
    public static void main(String[] args){  
        Receiver receiver = new Receiver();  
        Command command = new ConcreteCommand(receiver);  
        //客户端直接执行具体命令方式（此方式与类图相符）  
        command.execute();  
  
        //客户端通过调用者来执行命令  
        Invoker invoker = new Invoker();  
        invoker.setCommand(command);  
        invoker.action();  
    }  
}

3.解释器模式

加减乘除用4个基本单位表示

4. 观察者模式

5. 状态模式

对象的行为依赖于它的某些属性值，状态的改变将导致行为的变化。

class State(object):

    """Base state. This is to share functionality"""

    def scan(self):
        """Scan the dial to the next station"""
        self.pos += 1
        if self.pos == len(self.stations):
            self.pos = 0
        print(u"Scanning... Station is %s %s" %
              (self.stations[self.pos], self.name))


class AmState(State):

    def __init__(self, radio):
        self.radio = radio
        self.stations = ["1250", "1380", "1510"]
        self.pos = 0
        self.name = "AM"

    def toggle_amfm(self):
        print(u"Switching to FM")
        self.radio.state = self.radio.fmstate


class FmState(State):

    def __init__(self, radio):
        self.radio = radio
        self.stations = ["81.3", "89.1", "103.9"]
        self.pos = 0
        self.name = "FM"

    def toggle_amfm(self):
        print(u"Switching to AM")
        self.radio.state = self.radio.amstate


class Radio(object):

    """A radio.     It has a scan button, and an AM/FM toggle switch."""

    def __init__(self):
        """We have an AM state and an FM state"""
        self.amstate = AmState(self)
        self.fmstate = FmState(self)
        self.state = self.amstate

    def toggle_amfm(self):
        self.state.toggle_amfm()

    def scan(self):
        self.state.scan()


# Test our radio out
if __name__ == '__main__':
    radio = Radio()
    actions = [radio.scan] * 2 + [radio.toggle_amfm] + [radio.scan] * 2
    actions *= 2

    for action in actions:
        action()

### OUTPUT ###
# Scanning... Station is 1380 AM
# Scanning... Station is 1510 AM
# Switching to FM
# Scanning... Station is 89.1 FM
# Scanning... Station is 103.9 FM
# Scanning... Station is 81.3 FM
# Scanning... Station is 89.1 FM
# Switching to AM
# Scanning... Station is 1250 AM
# Scanning... Station is 1380 AM

6. 策略模式

class Strategy(object):
    """抽象算法类"""
    def AlgorithmInterface(self):
        raise NotImplementedError()

class ConcreteStrategyA(Strategy):
    def AlgorithmInterface(self):
        print '算法Ａ'

class ConcreteStrategyB(Strategy):
    def AlgorithmInterface(self):
        print '算法B'

class Context(object):
    """上下文，作用就是封装策略的实现细节，用户只需要知道有哪些策略可用"""
    def __init__(self, strategy):
        # 初始化时传入具体的策略实例
        self.strategy = strategy

    def ContextInterface(self):
        # 负责调用具体的策略实例的接口
        self.strategy.AlgorithmInterface()

def client(cond):
    # 策略模式的使用演示
    # 用户只需要根据不同的条件，将具体的算法实现类传递给Context，
    # 然后调用Context暴露给用户的接口就行了。
    if cond == 'A':
        context = Context(ConcreteStrategyA())
    elif cond == 'B':
        context = Context(ConcreteStrategyB())

    result = context.ContextInterface()

7. 模板模式

class Person(object):
    def Chew(self):
        """咀嚼食物"""
        raise NotImplementedError()

    def Swallow(self):
        print '咽下去'

    def Eat(self):
        # 吃饭分两步，先嚼，再咽。
        self.Chew()
        self.Swallow()

class Man(Person):
    def Chew(self):
        # 男人通常狼吞虎咽
        print '嚼三下'

class Woman(Person):
    def Chew(self):
        # 女人通常细嚼慢咽
        print '嚼六下'