from threading import Thread
import os


class InputData(object):
    def read(self):
        raise NotImplementedError


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

    def read(self):
        return open(self.path, encoding='utf8').read()


class Worker(object):
    def __init__(self, input_data):
        self.input_data = input_data
        self.result = 0

    def map(self):
        raise NotImplementedError

    def reduce(self, other):
        raise NotImplementedError


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

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


def generate_inputs(data_dir):
    for name in os.listdir(data_dir):
        yield PathInputData(os.path.join(data_dir, name))


def create_workers(input_list):
    workers = []
    print('input_list', input_list)
    for input_data in input_list:
        workers.append(LineCountWorker(input_data))
    return workers


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[0], workers[1:]
    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)


path = "D:\\python3.64\\CorePython\\chapter-6"
result = mapreduce(path)
print('There are', result, 'lines')

输出:

input_list <generator object generate_inputs at 0x00000278722C7BF8>
There are 83 lines

升级版:

from threading import Thread
import os


class GenericInputData(object):
    def read(self):
        raise NotImplementedError

    @classmethod
    def generate_inputs(cls, config):
        raise NotImplementedError


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

    def read(self):
        return open(self.path, encoding='utf-8').read()
    
    @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(object):
    def __init__(self, input_data):
        self.input_data = input_data
        self.result = 0

    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


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[0], workers[1:]
    for worker in rest:
        first.reduce(worker)
    return first.result


# 最后,重写mapreduce函数,令其变得完全通用.
def mapreduce(worker_class, input_class, config):
    workers = worker_class.create_workers(input_class, config)
    return execute(workers)
    # 在测试文件上面执行修改后的MapReduce程序,所得结果与原来那套实现方式是相同的
    # .区别在于,现在的mapreduce函数需要更多的参数,以便用更加通用的方式来梁作相关对象.


path = "D:\\python3.64\\CorePython\\chapter-6"
config = {'data_dir': path}
result = mapreduce(LineCountWorker, PathInputData, config)
print('There are', result, 'lines')

输出:
There are 83 lines