Book Image

Practical Data Wrangling

By : Allan Visochek
Book Image

Practical Data Wrangling

By: Allan Visochek

Overview of this book

Around 80% of time in data analysis is spent on cleaning and preparing data for analysis. This is, however, an important task, and is a prerequisite to the rest of the data analysis workflow, including visualization, analysis and reporting. Python and R are considered a popular choice of tool for data analysis, and have packages that can be best used to manipulate different kinds of data, as per your requirements. This book will show you the different data wrangling techniques, and how you can leverage the power of Python and R packages to implement them. You’ll start by understanding the data wrangling process and get a solid foundation to work with different types of data. You’ll work with different data structures and acquire and parse data from various locations. You’ll also see how to reshape the layout of data and manipulate, summarize, and join data sets. Finally, we conclude with a quick primer on accessing and processing data from databases, conducting data exploration, and storing and retrieving data quickly using databases. The book includes practical examples on each of these points using simple and real-world data sets to give you an easier understanding. By the end of the book, you’ll have a thorough understanding of all the data wrangling concepts and how to implement them in the best possible way.
Table of Contents (16 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Specifying input and output file names in the Terminal


So far, you have specified the file names directly inside the program. Alternatively, it is possible to write your program so that you can specify the names of the input and output files in the Terminal when the program is run. This is particularly useful if you need to run the same program several times with different input datasets and collect several different output files.

The sys module allows you to access an array of strings that correspond to the parameters entered in the Terminal when a program is run. To get a sense for how this works, you can use create a basic program as follows to import the sys module and print out the parameter array:

import sys
print(sys.argv)

You can specify parameters to the program after the initial Python command separated by spaces, as follows:

$Python(3) json_code.py arg1 arg2 asdf fdsa

When running the preceding command, you will see that the parameters that you specified become the elements of the...