Learn Python Programming Second Edition Fabrizio Romano

Learn Python Programming Second Edition

Dedication

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Foreword

Contributors

About the author

About the reviewers

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Preface

Who this book is for

What this book covers

To get the most out of this book

Download the example code files

Conventions used

Get in touch

Reviews

A Gentle Introduction to Python

A proper introduction

Enter the Python

About Python

Portability

Coherence

Developer productivity

An extensive library

Software quality

Software integration

Satisfaction and enjoyment

What are the drawbacks?

Who is using Python today?

Setting up the environment

Python 2 versus Python 3

Installing Python

Setting up the Python interpreter

About virtualenv

Your first virtual environment

Your friend, the console

How you can run a Python program

Running Python scripts

Running the Python interactive shell

Running Python as a service

Running Python as a GUI application

How is Python code organized?

How do we use modules and packages?

Python’s execution model

Names and namespaces

Scopes

Objects and classes

Guidelines on how to write good code

The Python culture

A note on IDEs

Summary

Built-in Data Types

Everything is an object

Mutable or immutable? That is the question

Numbers

Integers

Booleans

Real numbers

Complex numbers

Fractions and decimals

Immutable sequences

Strings and bytes

Encoding and decoding strings

Indexing and slicing strings

String formatting

Tuples

Mutable sequences

Lists

Byte arrays

Set types

Mapping types – dictionaries

The collections module

namedtuple

defaultdict

ChainMap

Enums

Final considerations

Small values caching

How to choose data structures

About indexing and slicing

About the names

Summary

Iterating and Making Decisions

Conditional programming

A specialized else – elif

The ternary operator

Looping

The for loop

Iterating over a range

Iterating over a sequence

Iterators and iterables

Iterating over multiple sequences

The while loop

The break and continue statements

A special else clause

Putting all this together

A prime generator

Applying discounts

A quick peek at the itertools module

Infinite iterators

Iterators terminating on the shortest input sequence

Combinatoric generators

Summary

Functions, the Building Blocks of Code

Why use functions?

Reducing code duplication

Splitting a complex task

Hiding implementation details

Improving readability

Improving traceability

Scopes and name resolution

The global and nonlocal statements

Input parameters

Argument-passing

Assignment to argument names doesn’t affect the caller

Changing a mutable affects the caller

How to specify input parameters

Positional arguments

Keyword arguments and default values

Variable positional arguments

Variable keyword arguments

Keyword-only arguments

Combining input parameters

Additional unpacking generalizations

Avoid the trap! Mutable defaults

Return values

Returning multiple values

A few useful tips

Recursive functions

Anonymous functions

Function attributes

Built-in functions

One final example

Documenting your code

Importing objects

Relative imports

Summary

Saving Time and Memory

The map, zip, and filter functions

map

zip

filter

Comprehensions

Nested comprehensions

Filtering a comprehension

dict comprehensions

set comprehensions

Generators

Generator functions

Going beyond next

The yield from expression

Generator expressions

Some performance considerations

Don’t overdo comprehensions and generators

Name localization

Generation behavior in built-ins

One last example

Summary

OOP, Decorators, and Iterators

Decorators

A decorator factory

Object-oriented programming (OOP)

The simplest Python class

Class and object namespaces

Attribute shadowing

Me, myself, and I – using the self variable

Initializing an instance

OOP is about code reuse

Inheritance and composition

Accessing a base class

Multiple inheritance

Method resolution order

Class and static methods

Static methods

Class methods

Private methods and name mangling

The property decorator

Operator overloading

Polymorphism – a brief overview

Data classes

Writing a custom iterator

Summary

Files and Data Persistence

Working with files and directories

Opening files

Using a context manager to open a file

Reading and writing to a file

Reading and writing in binary mode

Protecting against overriding an existing file

Checking for file and directory existence

Manipulating files and directories

Manipulating pathnames

Temporary files and directories

Directory content

File and directory compression

Data interchange formats

Working with JSON

Custom encoding/decoding with JSON

IO, streams, and requests

Using an in-memory stream

Making HTTP requests

Persisting data on disk

Serializing data with pickle

Saving data with shelve

Saving data to a database

Summary

Testing, Profiling, and Dealing with Exceptions

Testing your application

The anatomy of a test

Testing guidelines

Unit testing

Writing a unit test

Mock objects and patching

Assertions

Testing a CSV generator

Boundaries and granularity

Testing the export function

Final considerations

Test-driven development

Exceptions

Profiling Python

When to profile?

Summary

Cryptography and Tokens

The need for cryptography

Useful guidelines

Hashlib

Secrets

Random numbers

Token generation

Digest comparison

HMAC

JSON Web Tokens

Registered claims

Time-related claims

Auth-related claims

Using asymmetric (public-key) algorithms

Useful references

Summary

Concurrent Execution

Concurrency versus parallelism

Threads and processes – an overview

Quick anatomy of a thread

Killing threads

Context-switching

The Global Interpreter Lock

Race conditions and deadlocks

Race conditions

Scenario A – race condition not happening

Scenario B – race condition happening

Locks to the rescue

Scenario C – using a lock

Deadlocks

Quick anatomy of a process

Properties of a process

Multithreading or multiprocessing?

Concurrent execution in Python

Starting a thread

Starting a process

Stopping threads and processes

Stopping a process

Spawning multiple threads

Dealing with race conditions

A thread’s local data

Thread and process communication

Thread communication

Sending events

Inter-process communication with queues

Thread and process pools

Using a process to add a timeout to a function

Case examples

Example one – concurrent mergesort

Single-thread mergesort

Single-thread multipart mergesort

Multithreaded mergesort

Multiprocess mergesort

Example two – batch sudoku-solver

What is Sudoku?

Implementing a sudoku-solver in Python

Solving sudoku with multiprocessing

Example three – downloading random pictures

Downloading random pictures with asyncio

Summary

Debugging and Troubleshooting

Debugging techniques

Debugging with print

Debugging with a custom function

Inspecting the traceback

Using the Python debugger

Inspecting log files

Other techniques

Profiling

Assertions

Where to find information

Troubleshooting guidelines

Using console editors

Where to inspect

Using tests to debug

Monitoring

Summary

GUIs and Scripts

First approach – scripting

The imports

Parsing arguments

The business logic

Second approach – a GUI application

The imports

The layout logic

The business logic

Fetching the web page

Saving the images

Alerting the user

How can we improve the application?

Where do we go from here?

The turtle module

wxPython, PyQt, and PyGTK

The principle of least astonishment

Threading considerations

Summary

Data Science

IPython and Jupyter Notebook

Installing the required libraries

Using Anaconda

Starting a Notebook

Dealing with data

Setting up the Notebook

Preparing the data

Cleaning the data

Creating the DataFrame

Unpacking the campaign name

Unpacking the user data

Cleaning everything up

Saving the DataFrame to a file

Visualizing the results

Where do we go from here?

Summary

Web Development

What is the web?

How does the web work?

The Django web framework

Django design philosophy

The model layer

The view layer

The template layer

The Django URL dispatcher

Regular expressions

A regex website

Setting up Django

Starting the project

Creating users

Adding the Entry model

Customizing the admin panel

Creating the form

Writing the views

The home view

The entry list view

The form view

Tying up URLs and views

Writing the templates

The future of web development

Writing a Flask view

Building a JSON quote server in Falcon

Summary

Farewell

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