Book Image

NumPy Beginner's Guide - Second Edition

By : Ivan Idris
Book Image

NumPy Beginner's Guide - Second Edition

By: Ivan Idris

Overview of this book

NumPy is an extension to, and the fundamental package for scientific computing with Python. In today's world of science and technology, it is all about speed and flexibility. When it comes to scientific computing, NumPy is on the top of the list. NumPy Beginner's Guide will teach you about NumPy, a leading scientific computing library. NumPy replaces a lot of the functionality of Matlab and Mathematica, but in contrast to those products, is free and open source. Write readable, efficient, and fast code, which is as close to the language of mathematics as is currently possible with the cutting edge open source NumPy software library. Learn all the ins and outs of NumPy that requires you to know basic Python only. Save thousands of dollars on expensive software, while keeping all the flexibility and power of your favourite programming language.You will learn about installing and using NumPy and related concepts. At the end of the book we will explore some related scientific computing projects. This book will give you a solid foundation in NumPy arrays and universal functions. Through examples, you will also learn about plotting with Matplotlib and the related SciPy project. NumPy Beginner's Guide will help you be productive with NumPy and have you writing clean and fast code in no time at all.
Table of Contents (19 chapters)
Numpy Beginner's Guide Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – loading from CSV files


How do we deal with CSV files? Luckily, the loadtxt function can conveniently read CSV files, split up the fields, and load the data into NumPy arrays. In the following example, we will load historical price data for Apple (the company, not the fruit). The data is in the CSV format. The first column contains a symbol that identifies the stock. In our case, it is AAPL. Second is the date in the dd-mm-yyyy format. The third column is empty. Then, in order, we have the open, high, low, and close price. Last, but not least, is the volume of the day. This is what a line looks like:

AAPL,28-01-2011, ,344.17,344.4,333.53,336.1,21144800

For now, we are only interested in the close price and volume. In the preceding sample, that would be 336.1 and 21144800. Store the close price and volume in two arrays, as follows:

c,v=np.loadtxt('data.csv', delimiter=',', usecols=(6,7), unpack=True)

As you can see, data is stored in the data.csv file. We have set the delimiter...