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 CSV files

The read_csv method of the pandas library can be used to read a file with comma separated values (CSV) and load it into memory as a pandas data frame. In this recipe, we read a CSV file and address some common issues: creating column names that make sense to us, parsing dates, and dropping rows with critical missing data.

Raw data is often stored as CSV files. These files have a carriage return at the end of each line of data to demarcate a row, and a comma between each data value to delineate columns. Something other than a comma can be used as the delimiter, such as a tab. Quotation marks may be placed around values, which can be helpful when the delimiter occurs naturally within certain values, which sometimes happens with commas.

All data in a CSV file are characters, regardless of the logical data type. This is why it is easy to view a CSV file, presuming it is not too large, in a text editor. The pandas read_csv method will make an educated guess about...