Introduction

We cannot begin a book on Spark (well, on PySpark) without first specifying what Spark is. Spark is a powerful, flexible, open source, data processing and querying engine. It is extremely easy to use and provides the means to solve a huge variety of problems, ranging from processing unstructured, semi-structured, or structured data, through streaming, up to machine learning. With over 1,000 contributors from over 250 organizations (not to mention over 3,000 Spark Meetup community members worldwide), Spark is now one of the largest open source projects in the portfolio of the Apache Software Foundation.

The origins of Spark can be found in 2012 when it was first released; Matei Zacharia developed the first versions of the Spark processing engine at UC Berkeley as part of his PhD thesis. Since then, Spark has become extremely popular, and its popularity stems from a number of reasons:

• It is fast: It is estimated that Spark is 100 times faster than Hadoop when working purely in memory, and around 10 times faster when reading or writing data to a disk.
• It is flexible: You can leverage the power of Spark from a number of programming languages; Spark natively supports interfaces in Scala, Java, Python, and R. 
• It is extendible: As Spark is an open source package, you can easily extend it by introducing your own classes or extending the existing ones. 
• It is powerful: Many machine learning algorithms are already implemented in Spark so you do not need to add more tools to your stack—most of the data engineering and data science tasks can be accomplished while working in a single environment.
• It is familiar: Data scientists and data engineers, who are accustomed to using Python's pandas, or R's data.frames or data.tables, should have a much gentler learning curve (although the differences between these data types exist). Moreover, if you know SQL, you can also use it to wrangle data in Spark!
• It is scalable: Spark can run locally on your machine (with all the limitations such a solution entails). However, the same code that runs locally can be deployed to a cluster of thousands of machines with little-to-no changes. 

For the remainder of this book, we will assume that you are working in a Unix-like environment such as Linux (throughout this book, we will use Ubuntu Server 16.04 LTS) or macOS (running macOS High Sierra); all the code provided has been tested in these two environments. For this chapter (and some other ones, too), an internet connection is also required as we will be downloading a bunch of binaries and sources from the internet. 

We will not be focusing on installing Spark in a Windows environment as it is not truly supported by the Spark developers. However, if you are inclined to try, you can follow some of the instructions you will find online, such as from the following link: http://bit.ly/2Ar75ld.

Knowing how to use the command line and how to set some environment variables on your system is useful, but not really required—we will guide you through the steps.