Book Image

Python Data Cleaning Cookbook

By : Michael Walker
Book Image

Python Data Cleaning Cookbook

By: Michael Walker

Overview of this book

Getting clean data to reveal insights is essential, as directly jumping into data analysis without proper data cleaning may lead to incorrect results. This book shows you tools and techniques that you can apply to clean and handle data with Python. You'll begin by getting familiar with the shape of data by using practices that can be deployed routinely with most data sources. Then, the book teaches you how to manipulate data to get it into a useful form. You'll also learn how to filter and summarize data to gain insights and better understand what makes sense and what does not, along with discovering how to operate on data to address the issues you've identified. Moving on, you'll perform key tasks, such as handling missing values, validating errors, removing duplicate data, monitoring high volumes of data, and handling outliers and invalid dates. Next, you'll cover recipes on using supervised learning and Naive Bayes analysis to identify unexpected values and classification errors, and generate visualizations for exploratory data analysis (EDA) to visualize unexpected values. Finally, you'll build functions and classes that you can reuse without modification when you have new data. By the end of this Python book, you'll be equipped with all the key skills that you need to clean data and diagnose problems within it.
Table of Contents (12 chapters)

Using subsetting to examine logical inconsistencies in variable relationships

At a certain point, data issues come down to deductive logic problems, such as variable x has to be greater than some quantity a when variable y is less than some quantity b. Once we are through some initial data cleaning, it is important to check for logical inconsistencies. pandas makes this kind of error checking relatively straightforward with subsetting tools such as loc and Boolean indexing. This can be combined with summary methods on series and data frames to allow us to easily compare values for a particular row to values for the whole dataset or some subset of rows. We can also easily aggregate over columns. Just about any question we might have about the logical relationships between variables can be answered with these tools. We work through some examples in this recipe.

Getting ready

We will work with the National Longitudinal Survey of Youth (NLS), mainly with data on employment and education...