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Distributed Computing with Python
Distributed Computing with Python

Distributed Computing with Python: Harness the power of multiple computers using Python through this fast-paced informative guide

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Distributed Computing with Python

Chapter 2. Asynchronous Programming

In this chapter, we are finally going to write some code! The code in this chapter and all the chapters that follow is written for Python 3.5 (the current release at the time of writing). When modules, syntaxes, or language constructs are not available in earlier versions of Python (for example, Python 2.7), these will be pointed out in this chapter. In general, however, the code presented here should work on Python 2.x with some minor modifications.

Let's go back to some of the ideas presented in the previous chapter. We know that we can structure our algorithms and programs so that they can run on a local machine or on one or more computers across a network. Even when our code runs on a single machine, as we saw, we can use multiple threads and/or multiple processes so that its various parts can run at the same time on multiple CPUs.

We will now pause thinking about multiple CPUs and instead look at a single thread/process of execution...

Coroutines

In Python, the key to being able to suspend the execution of a function midway through is the use of coroutines, as we will see in this section. In order to understand coroutines, one needs to understand generators, and in order to understand those, one needs to have a grasp of iterators!

Most Python programmers are familiar with the concept of iterating some sort of collection (for example, strings, lists, tuples, file objects, and so on):

>>> for i in range(3):
...     print(i)
... 
0
1
2
>>> for line in open('exchange_rates_v1.py'):
...     print(line, end='')
... 
#!/usr/bin/env python3
import itertools
import time
import urllib.request

The reason why we can iterate all sorts of objects and not just lists or strings is the iteration protocol. The iteration protocol defines a standard interface for iteration: an object that implements __iter__ and __next__ (or __iter__ and next in Python 2.x) is an iterator and, as the name suggests...

An asynchronous example

To keep things simple but still interesting, let's write a tool that, given a text file, will count the occurrences of a given word. This example builds on the silly coroutine that we implemented in the previous section, adding some useful behavior to it.

It should be noted that, at least on a Linux or Mac OS X machine, one can achieve the same result very simply using the grep command, as we will see. Let's start by downloading a significantly large text that we will use as input data for our experiments. Let's just choose a public domain book from Project Gutenberg: War and Peace by Leo Tolstoy, which is freely available at http://www.gutenberg.org/cache/epub/2600/pg2600.txt.

The following snippet shows how we can download this text very easily:

$ curl -sO http://www.gutenberg.org/cache/epub/2600/pg2600.txt
$ wc pg2600.txt
   65007  566320 3291648 pg2600.txt

Next, we will start by counting the number of occurrences of the word love, regardless of case...

Summary

Python has had support for asynchronous programming since version 1.5.2, with the introduction of the asyncore and asynchat modules for asynchronous network programming. Version 2.5 introduced the ability to send data to coroutines via yield expressions, allowing us to write asynchronous code in a simpler but more powerful way. Python 3.4 introduced a new library for asynchronous I/O called asyncio.

Python 3.5 introduced true coroutine types via async def and await. Interested readers are encouraged to explore these new developments. One word of warning though: asynchronous programming is a powerful tool that can dramatically improve the performance of I/O-intensive code. It does not come without issues, though, the main of which is complexity.

Any important asynchronous code has to carefully select nonblocking libraries in order to avoid using blocking code. It has to implement a coroutine scheduler (since the OS does not schedule coroutines for us like it does with threads), which...

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Key benefits

  • You'll learn to write data processing programs in Python that are highly available, reliable, and fault tolerant
  • Make use of Amazon Web Services along with Python to establish a powerful remote computation system
  • Train Python to handle data-intensive and resource hungry applications

Description

CPU-intensive data processing tasks have become crucial considering the complexity of the various big data applications that are used today. Reducing the CPU utilization per process is very important to improve the overall speed of applications. This book will teach you how to perform parallel execution of computations by distributing them across multiple processors in a single machine, thus improving the overall performance of a big data processing task. We will cover synchronous and asynchronous models, shared memory and file systems, communication between various processes, synchronization, and more.

Who is this book for?

This book is for Python developers who have developed Python programs for data processing and now want to learn how to write fast, efficient programs that perform CPU-intensive data processing tasks.

What you will learn

  • Get an introduction to parallel and distributed computing
  • See synchronous and asynchronous programming
  • Explore parallelism in Python
  • Distributed application with Celery
  • Python in the Cloud
  • Python on an HPC cluster
  • Test and debug distributed applications

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Apr 12, 2016
Length: 170 pages
Edition : 1st
Language : English
ISBN-13 : 9781785889691
Languages :

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Product Details

Publication date : Apr 12, 2016
Length: 170 pages
Edition : 1st
Language : English
ISBN-13 : 9781785889691
Languages :

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Table of Contents

9 Chapters
1. An Introduction to Parallel and Distributed Computing Chevron down icon Chevron up icon
2. Asynchronous Programming Chevron down icon Chevron up icon
3. Parallelism in Python Chevron down icon Chevron up icon
4. Distributed Applications – with Celery Chevron down icon Chevron up icon
5. Python in the Cloud Chevron down icon Chevron up icon
6. Python on an HPC Cluster Chevron down icon Chevron up icon
7. Testing and Debugging Distributed Applications Chevron down icon Chevron up icon
8. The Road Ahead Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3
(3 Ratings)
5 star 66.7%
4 star 0%
3 star 33.3%
2 star 0%
1 star 0%
Hugo Jun 20, 2021
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Es werden die wichtigsten Mechanismen des distributed/parallel computing gut erklärt.
Amazon Verified review Amazon
Stefan Mar 23, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I needed a crash course on distributed programming and I got it out of this book. I had a week to learn about concurrency, threading, multiprocessing and how they are implemented in Python and I suceeded with this. I feel confident to jump into harder texts and tutorials and other frameworks now. This book will *not* give you an in-depth coverage of the topics, it is only about 120 pages of content. Perfect for my purpose, thank you.
Amazon Verified review Amazon
Phil Dec 18, 2017
Full star icon Full star icon Full star icon Empty star icon Empty star icon 3
This is a very light introduction to distributed computing with Python, which could really do with more information. It introduces important concepts but then moves straight on without getting into any detail. (ie. it mentions two communication methods between processes in the multiprocessing module, pipes and queues, and then ignores pipes altogether). If you've never touched distributing computing this might be a good starting point, but the python docs for the modules give far more detail and are almost as accessible (and free). Additionally there are quite a few errors in the book, at least one of which says the exact opposite of what it should, which might be very confusing for a reader.
Amazon Verified review Amazon
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