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.

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Table of Contents (21 chapters)
Title Page
Title Page
Credits
Credits
About the Authors
About the Authors
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Preface
Preface
Free Chapter
1
Getting started
Getting started
Obtaining and installing Python 3
Starting Python command line REPL
Leaving the REPL
Code structure and significant indentation
Python culture
Importing standard library modules
Getting help()
Scalar data types: integers, floats, None and bool
Relational operators
Control flow: if-statements and while-loops
Summary
2
Strings and Collections
Strings and Collections
str – an immutable sequence of Unicode code points
Moment of zen
Strings with Unicode
The bytes type  – an immutable sequence of bytes
list – a sequence of objects
The dict type – associating keys with values
The For-loops – iterating over series of items
Putting it all together
Summary
3
Modularity
Modularity
Organizing code in a .py file
Defining functions
Organizing our module into functions
The Python execution model
Setting up a main function with command line argument
Moment of zen
Docstrings
Comments
Shebang
4
Built-in types and the object model
Built-in types and the object model
The nature of Python object references
Argument passing semantics – pass by object-reference
Python return semantics
Function arguments in detail
The Python type system
Variable declaration and scoping
Scopes in action
Moment of zen
Everything is an object
Summary
5
Exploring Built-in Collection types
Exploring Built-in Collection types
tuple – an immutable sequence of objects
The tuple constructor
Strings in action
Moment of zen
range – a collection of evenly spaced integers
list in action
Dictionaries
set – an unordered collection of unique elements
Collection protocols
Summary
6
Exceptions
Exceptions
Exceptions and control flow
Handling multiple exceptions
Programmer errors
Empty blocks – the pass statement
Exception objects
Imprudent return codes
Re-raising exceptions
Exceptions are part of your function's API
Guard clauses
Exceptions, APIs, and protocols
Choosing not to guard against TypeError
Pythonic style – EAFP versus LBYL
Clean-up actions
Moment of zen
Platform-specific code
Summary
7
Comprehensions, iterables, and generators
Comprehensions, iterables, and generators
Comprehensions
Moment of zen
Iteration protocols
Generator functions
Generator expressions
8
Defining new types with classes
Defining new types with classes
Defining classes
Instance methods
Instance initializers
Validation and invariants
Adding a second class
Collaborating classes
Moment of zen
Booking seats
Naming methods for implementation details
Sometimes the only object you need is a function
Polymorphism and duck-typing
Inheritance and implementation sharing
Summary
9
Files and Resource Management
Files and Resource Management
Files
Context Managers
Moment of zen
Binary files
10
Unit testing with the Python standard library
Unit testing with the Python standard library
Test cases
Fixtures
Assertions
Unit testing example: text analysis
Using fixtures to create temporary files
Using the new fixtures
Using assertions to test behavior
Testing for exceptions
Testing for file existence
Moment of zen
Summary
11
Debugging with PDB
Debugging with PDB
Debugging commands
Palindrome debugging
Summary
12
Afterword – Just the Beginning
Afterword – Just the Beginning
13
Virtual Environments
Virtual Environments
Creating a virtual environment
Activating a virtual environment
Deactivating a virtual environment
Other tools for working with virtual environments
14
Packaging and Distribution
Packaging and Distribution
Configuring a package with distutils
Installing with distutils
Packaging with distutils
15
Installing Third-Party Packages
Installing Third-Party Packages
Installing pip
The Python Package Index
Installing Local Packages with pip
Uninstalling Packages

Chapter 13. Virtual Environments

A virtual environment is a light-weight, self-contained Python installation. The main motivation for virtual environments is to allow different projects to have control over the versions of installed Python packages, without interfering with other Python projects installed on the same host. A virtual environment consists of a directory containing a symbolic link to (Unix), or a copy of (Windows), an existing Python installation, together with an empty site-packages directory into which Python packages specific to this virtual environment can be installed. A second motivation for virtual environments is that users can create a virtual environment without needing administrator rights on their system, making it easy for them to install packages locally. A third motivation is that different virtual environments can be based on different versions of Python, making it easier to test code on say Python 3.4 and Python 3.5 on the same computer.

If you're using Python...

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