Book Image

Learning Python

By : Fabrizio Romano
Book Image

Learning Python

By: Fabrizio Romano

Overview of this book

Learning Python has a dynamic and varied nature. It reads easily and lays a good foundation for those who are interested in digging deeper. It has a practical and example-oriented approach through which both the introductory and the advanced topics are explained. Starting with the fundamentals of programming and Python, it ends by exploring very different topics, like GUIs, web apps and data science. The book takes you all the way to creating a fully fledged application. The book begins by exploring the essentials of programming, data structures and teaches you how to manipulate them. It then moves on to controlling the flow of a program and writing reusable and error proof code. You will then explore different programming paradigms that will allow you to find the best approach to any situation, and also learn how to perform performance optimization as well as effective debugging. Throughout, the book steers you through the various types of applications, and it concludes with a complete mini website built upon all the concepts that you learned.
Table of Contents (20 chapters)
Learning Python
Credits
About the Author
Acknowledgements
About the Reviewers
www.PacktPub.com
Preface
Index

Exceptions


Even though I haven't formally introduced them to you, by now I expect you to at least have a vague idea of what an exception is. In the previous chapters, we've seen that when an iterator is exhausted, calling next on it raises a StopIteration exception. We've met IndexError when we tried accessing a list at a position that was outside the valid range. We've also met AttributeError when we tried accessing an attribute on an object that didn't have it, and KeyError when we did the same with a key and a dictionary. We've also just met AssertionError when running tests.

Now, the time has come for us to talk about exceptions.

Sometimes, even though an operation or a piece of code is correct, there are conditions in which something may go wrong. For example, if we're converting user input from string to int, the user could accidentally type a letter in place of a digit, making it impossible for us to convert that value into a number. When dividing numbers, we may not know in advance...