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#!/usr/bin/env PYTHONHASHSEED=1234 python3
# Copyright 2014-2019 Brett Slatkin, Pearson Education Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#     http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Reproduce book environment
import random
random.seed(1234)
import logging
from pprint import pprint
from sys import stdout as STDOUT
# Write all output to a temporary directory
import atexit
import tempfile
TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)
# Make sure Windows processes exit cleanly
OLD_CWD = os.getcwd()
atexit.register(lambda: os.chdir(OLD_CWD))
os.chdir(TEST_DIR.name)
def close_open_files():
    everything = gc.get_objects()
    for obj in everything:
        if isinstance(obj, io.IOBase):
            obj.close()
atexit.register(close_open_files)
# Example 1
class InputData:
    def read(self):
        raise NotImplementedError
# Example 2
class PathInputData(InputData):
    def __init__(self, path):
        super().__init__()
        self.path = path
    def read(self):
        with open(self.path) as f:
            return f.read()
# Example 3
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
# Example 4
class LineCountWorker(Worker):
    def map(self):
        data = self.input_data.read()
        self.result = data.count('\n')
    def reduce(self, other):
        self.result += other.result
# Example 5
def generate_inputs(data_dir):
    for name in os.listdir(data_dir):
        yield PathInputData(os.path.join(data_dir, name))
# Example 6
def create_workers(input_list):
    workers = []
    for input_data in input_list:
        workers.append(LineCountWorker(input_data))
    return workers
# Example 7
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
# Example 8
def mapreduce(data_dir):
    inputs = generate_inputs(data_dir)
    workers = create_workers(inputs)
    return execute(workers)
# Example 9
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')
# Example 10
class GenericInputData:
    def read(self):
        raise NotImplementedError
    @classmethod
    def generate_inputs(cls, config):
        raise NotImplementedError
# Example 11
class PathInputData(GenericInputData):
    def __init__(self, path):
        super().__init__()
        self.path = path
    def read(self):
        with open(self.path) as f:
            return f.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))
# Example 12
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
# Example 13
class LineCountWorker(GenericWorker):
    def map(self):
        data = self.input_data.read()
        self.result = data.count('\n')
    def reduce(self, other):
        self.result += other.result
# Example 14
def mapreduce(worker_class, input_class, config):
    workers = worker_class.create_workers(input_class, config)
    return execute(workers)
# Example 15
config = {'data_dir': tmpdir}
result = mapreduce(LineCountWorker, PathInputData, config)
print(f'There are {result} lines')
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