Python中通过@classmethod 实现多态的示例

# 接收输入信息类体系
class InputData:
    def read(self):
        raise NotImplementedError

class PathInputData(InputData):
    def __init__(self,path):
        super().__init__()
        self.path = path

    def read(self):
        with open(self.path) as f:
            return f.read()

# 处理信息类体系
class Worker:
    def __init__(self, input_data):
        self.input_data = input_data
        self.result = None

    def map(self):
        raise NotImplementedError

    def reduce(self, other):
        raise NotImplementedError

class LineCountWorker(Worker):
    def map(self):
        data = self.input_data
        self.result = data.count('/n')

    def reduce(self, other):
        self.result += other.result

# 组合业务
import os
def generate_inputs(data_dit):
    for name in os.listdir(data_dit):
        # 读文件内容
        yield PathInputData(os.path.join(data_dit, name))

def create_workers(input_list):
    workers = []
    for input_data in input_list:
        # 处理数据
        workers.append(LineCountWorker(input_data))
    return workers

from threading import Thread
def execute(workers):
    threads = [Thread(target=w.map) for w in workers]
    for thread in threads: thread.start()
    for thread in threads: thread.join()

    first, *rest = workers
    for worker in rest:
        first.reduce(worker)
    return first.result

def mapreduce(data_dir):
    inputs = generate_inputs(data_dir)
    workers = create_workers(inputs)
    return execute(workers)

import os
import random
def write_test_files(tmpdir):
    os.makedirs(tmpdir)
    for i in range(100):
        with open(os.path.join(tmpdir, str(i)), 'w') as f:
            f.write('\n' * random.randint(0, 100))
tmpdir = 'test_inputs'
write_test_files(tmpdir)
result = mapreduce(tmpdir)
print(f'There are  {result} lines')

class GenericInputData:
    def read(self):
        raise NotImplementedError
	# 创建一个多态的类方法，让子类实现不同的功能
    @classmethod
    def generate_inputs(cls, config):
        raise NotImplementedError

class PathInputData(GenericInputData):
    def __init__(self, path):
        super().__init__()
        self.path = path

    def read(self):
        with open(self.path) as f:
            return f.read()
	# 子类重写父类的类方法
    @classmethod
    def generate_inputs(cls, config):
        data_dir = config['data_dir']
        for name in os.listdir(data_dir):
            yield cls(os.path.join(data_dir, name))


class GenericWorker:
    def __init__(self, input_data):
        self.input_data = input_data
        self.result = None

    def map(self):
        raise NotImplementedError

    def reduce(self, other):
        raise NotImplementedError

    @classmethod
    def create_workers(cls, input_class, config):
        workers = []
        for input_data in input_class.generate_inputs(config):
            workers.append(cls(input_data))
        return workers

class LineCountWorker(GenericWorker):
    def map(self):
        data = self.input_data.read()
        self.result = data.count('\n')

    def reduce(self, other):
        self.result += other.result

# 定义的形参类型为父类，实现了类方法多态
def mapreduce(worker_class, input_class, config):
    workers = worker_class.create_workers(input_class, config)
    return execute(workers)
config = {'data_dir': tmpdir}
result = mapreduce(LineCountWorker, PathInputData, config)
print(f'There are {result} lines')