Book Image

The Python Apprentice

By : Robert Smallshire, Austin Bingham
Book Image

The Python Apprentice

By: Robert Smallshire, Austin Bingham

Overview of this book

Experienced programmers want to know how to enhance their craft and we want to help them start as apprentices with Python. We know that before mastering Python you need to learn the culture and the tools to become a productive member of any Python project. Our goal with this book is to give you a practical and thorough introduction to Python programming, providing you with the insight and technical craftsmanship you need to be a productive member of any Python project. Python is a big language, and it’s not our intention with this book to cover everything there is to know. We just want to make sure that you, as the developer, know the tools, basic idioms and of course the ins and outs of the language, the standard library and other modules to be able to jump into most projects.
Table of Contents (21 chapters)
Title Page
Credits
About the Authors
www.PacktPub.com
Customer Feedback
Preface
12
Afterword – Just the Beginning

The nature of Python object references


In previous chapters we've already talked about and used "variables" in Python, but what exactly is a variable? Consider something as straightforward as assigning an integer to a variable:

>>> x = 1000

What's really happening when we do this? First, Python creates an int object  with a value of 1000. This object is anonymous in the sense that it doesn't, in and of itself, have a name (x or otherwise). It's simply an object allocated and tracked by the Python runtime system.

After creating the object, Python then creates an object reference with the name x and arranges for x to refer to the int(1000) object:

Figure 4.1:  Assign the name 'x' to an integer object with the value 1000

Reassigning a reference

Now we'll modify the value of x with another assignment:

>>> x = 500

This does not result any sort of change to the int(1000) object we previously constructed. Integer objects in Python are immutable and cannot be changed. In fact, what happens...