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)

Importing data from SQL databases

In this recipe, we will use pymssql and mysql apis to read data from Microsoft SQL Server and MySQL (now owned by Oracle) databases, respectively. Data from sources such as these tends to be well structured since it is designed to facilitate simultaneous transactions by members of organizations, and those who interact with them. Each transaction is also likely related to some other organizational transaction.

This means that although data tables from enterprise systems are more reliably structured than data from CSV files and Excel files, their logic is less likely to be self-contained. You need to know how the data from one table relates to data from another table to understand its full meaning. These relationships need to be preserved, including the integrity of primary and foreign keys, when pulling data. Moreover, well-structured data tables are not necessarily uncomplicated data tables. There are often sophisticated coding schemes that determine...