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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The no-nonsense way to get started coding in the Python programming language
Python Essentials For Dummies is a quick reference to all the core concepts in Python, the multifaceted general-purpose language used for everything from building websites to creating apps. This book gets right to the point, with no excess review, wordy explanations, or fluff, making it perfect as a desk reference on the job or as a brush-up as you expand your skills in related areas. Focusing on just the essential topics you need to know to brush up or level up your Python skill, this is the reliable little book you can always turn to for answers.
- Get a quick and thorough intro to the basic concepts of coding in Python
- Review what you've already learned or pick up essential new skills
- Create websites, software, machine learning, and automation for school or work
- Keep this concise reference book handy for jogging your memory as you code
This portable Dummies Essentials book focuses on the key topics you need to know about the popular Python language. Great for supplementing a course, reviewing for a certification, or staying knowledgeable on the job.
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Seitenzahl: 231
Veröffentlichungsjahr: 2024
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Python® Essentials For Dummies®
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Table of Contents
Cover
Title Page
Copyright
Introduction
About This Book
Foolish Assumptions
Icons Used in This Book
Where to Go from Here
Chapter 1: Starting with Python
Why Python Is Hot
Choosing the Right Python
Tools for Success
Chapter 2: Using Interactive Mode, Getting Help, and Writing Apps
Using Python’s Interactive Mode
Creating a Folder for Your Python Code
Typing, Editing, and Debugging Python Code
Chapter 3: Python Elements and Syntax
The Zen of Python
Introducing Object-Oriented Programming
Discovering Why Indentations Count, Big Time
Using Python Modules
Chapter 4: Building Your First Python Application
Opening the Python App File
Typing and Using Python Comments
Understanding Python Data Types
Working with Python Operators
Creating and Using Variables
Understanding What Syntax Is and Why It Matters
Chapter 5: Working with Numbers, Text, and Dates
Calculating Numbers with Functions
Still More Math Functions
Formatting Numbers
Grappling with Weirder Numbers
Manipulating Strings
Uncovering Dates and Times
Chapter 6: Controlling the Action
Main Operators for Controlling the Action
Making Decisions with if
Repeating a Process with for
Looping with while
Chapter 7: Speeding Along with Lists and Tuples
Defining and Using Lists
What’s a Tuple and Who Cares?
Working with Sets
Chapter 8: Wrangling Bigger Chunks of Code
Creating a Function
Commenting a Function
Passing Information to a Function
Returning Values from Functions
Chapter 9: Sidestepping Errors
Understanding Exceptions
Handling Errors Gracefully
Being Specific about Exceptions
Keeping Your App from Crashing
Adding an else to the Mix
Using try … except … else … finally
Raising Your Own Exceptions
Chapter 10: Working with External Files
Understanding Text and Binary Files
Opening and Closing Files
Reading a File’s Contents
Looping through a File
Reading and Copying a Binary File
Chapter 11: Juggling JSON Data
Organizing JSON Data
Understanding Serialization
Loading Data from JSON Files
Dumping Python Data to JSON
Chapter 12: Interacting with the Internet
Seeing How the Web Works
Chapter 13: Libraries, Packages, and Modules
Understanding the Python Standard Library
Exploring Python Packages
Importing Python Modules
Chapter 14: The Ten Most Essential Aspects of Python
Being Pythonic
Identifying the Importance of Indents
Understanding Python Syntax
Appreciating the Flexibility of Python Variables
Seeing Lists as Your Friend
Controlling Your Program
Understanding Python Functions
Figuring Out Errors
Using Other People’s Modules
Using the Web and AI When You Have Problems
Index
About the Authors
Connect with Dummies
End User License Agreement
List of Tables
Chapter 4
TABLE 4-1 Python’s Arithmetic Operators
TABLE 4-2 Python Comparison Operators
TABLE 4-3 Python Boolean Operators
Chapter 5
TABLE 5-1 Some Built-In Python Functions for Numbers
TABLE 5-2 Some Functions from the Python Math Module
TABLE 5-3 Python for Base 2, 8, and 16 Numbers
TABLE 5-4 Python Sequence Operators That Work with Strings
TABLE 5-5 Built-In Methods for Python 3 Strings
TABLE 5-6 Sample Date Format Strings
TABLE 5-7 Sample Datetime Format Strings
Chapter 6
TABLE 6-1 Python Comparison Operators for Decision-Making
TABLE 6-2 Python Logical Operators
Chapter 7
TABLE 7-1 Methods for Working with Lists
Chapter 11
TABLE 11-1 Python JSON Methods for Serializing and Deserializing JSON Data
TABLE 11-2 Python and JSON Data Conversions
Chapter 12
TABLE 12-1 Common HTTP Status Codes
TABLE 12-2 Packages from the Python urllib Library
List of Illustrations
Chapter 1
FIGURE 1-1: Obtaining the Python extension in VS Code.
FIGURE 1-2: The GitHub Copilot extension in VS Code.
FIGURE 1-3: The Accounts and Copilot icons in VS Code.
Chapter 2
FIGURE 2-1: The Terminal pane in VS Code.
FIGURE 2-2: Python doesn’t know what
howdy
means.
FIGURE 2-3: Keyword help.
FIGURE 2-4: The
hello.py
file contains some Python code and has unsaved changes...
FIGURE 2-5: Output from
hello.py
.
FIGURE 2-6:
is typed incorrectly in
hello.py
.
Chapter 3
FIGURE 3-1: The Zen of Python.
Chapter 4
FIGURE 4-1: The
hello.py
file, open for editing in VS Code.
FIGURE 4-2: The 19.9 is the output from
print(extended_price)
in the code.
Chapter 5
FIGURE 5-1: Using the
sqrt()
function from the
math
module.
FIGURE 5-2: A super simple f-string for formatting.
Chapter 6
FIGURE 6-1: The result of a simple
if
when the condition proves true.
FIGURE 6-2: Print an initial greeting based on the time of day.
FIGURE 6-3: Looping through a list.
FIGURE 6-4: Nested loops.
FIGURE 6-5: An infinite
while
loop.
FIGURE 6-6: A
while
loop with
continue
.
Chapter 7
FIGURE 7-1: Seeing whether an item is in a list.
FIGURE 7-2: Program fails when trying to find the index of a nonexistent list i...
Chapter 8
FIGURE 8-1: Writing, and calling, a simple function named
hello()
.
FIGURE 8-2: A sample function with a couple of comments added.
FIGURE 8-3: Passing data to a function via a variable.
FIGURE 8-4: The
hello
function with three parameters.
FIGURE 8-5: Calling the
hello()
function with three parameters, and again with ...
FIGURE 8-6: Calling a function with keyword arguments (kwargs).
FIGURE 8-7: A function accepting any number of arguments with
*args
.
FIGURE 8-8: Printing a string returned by the
alphabetize()
function.
Chapter 9
FIGURE 9-1: The
showfilecontents.py
and
people.csv
files in a folder in VS Code...
FIGURE 9-2: The contents of the
people.csv
file in Excel (top) and a text edito...
FIGURE 9-3: The
showfilecontents.py
file raises an exception.
FIGURE 9-4: The
showfilecontents.py
file catches the error and displays a frien...
FIGURE 9-5: The correct error message is displayed.
FIGURE 9-6: Code with try, exception handlers, and an
else:
block for when ther...
Chapter 10
FIGURE 10-1: Common text and binary files.
FIGURE 10-2: The
binarycopy.py
file copies any binary file.
FIGURE 10-3: Running
binarycopy.py
added
happy_pickle_copy.jpg
to the folder.
Chapter 11
FIGURE 11-1: Some data in an Excel spreadsheet.
FIGURE 11-2: Excel spreadsheet data converted to JSON format.
FIGURE 11-3: Some data in a Google Firebase Realtime Database.
FIGURE 11-4: Output from showing one value at a time from each dictionary (see ...
FIGURE 11-5: Changing the value of one key in each dictionary, and removing an ...
Chapter 12
FIGURE 12-1: The client makes a request, and the server sends back a response.
FIGURE 12-2: Different parts of URLs.
FIGURE 12-3: Inspecting HTTP headers with Google Chrome.
FIGURE 12-4: HTTP headers.
FIGURE 12-5: Sample page used for web scraping.
FIGURE 12-6: Some of the code from the sample page for web scraping.
FIGURE 12-7: Web scraping code complete.
Chapter 13
FIGURE 13-1: Python’s built-in functions.
Guide
Cover
Table of Contents
Title Page
Copyright
Begin Reading
Index
About the Authors
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Python® Essentials For Dummies®
Published by: John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, www.wiley.com
Copyright © 2024 by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
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Trademarks: Wiley, For Dummies, the Dummies Man logo, Dummies.com, Making Everything Easier, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and may not be used without written permission. Python is a registered trademark of Python Software Foundation Corporation. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not associated with any product or vendor mentioned in this book.
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Library of Congress Control Number: 2024934008
ISBN 978-1-394-26347-9 (pbk); ISBN 978-1-394-26348-6 (ebk); ISBN 978-1-394-26349-3 (ebk)
Introduction
The Python language is becoming more and more popular, and in 2017 it became the most popular language in the world according to IEEE Spectrum. The power of Python is real.
Python is the number-one language because it’s easy to learn and use, due partly to its simplified syntax and natural-language flow but also to the amazing user community and the breadth of applications available.
About This Book
This book is a reference manual to guide you through the process of learning the essentials of Python. If you’re looking to learn a little about a lot of exciting things, this is the book for you. It gives you an introduction to the topics that you’ll need to explore more deeply.
This is a hands-on book, with examples and code throughout. You’ll enter the code, run it, and then modify it to do what you want.
In this book, we take you through the basics of the Python language in small, easy-to-understand steps.
Foolish Assumptions
We assume that you know how to use a computer in a basic way. If you can turn on the computer and use a mouse, you’re ready for this book. We assume that you don’t know how to program yet, although you will have some skills in programming after reading this book.
Icons Used in This Book
What’s a For Dummies book without icons pointing you in the direction of truly helpful information that’s sure to speed you along your way? Here we briefly describe each icon we use in this book.
The Tip icon points out helpful information that’s likely to make your job easier.
The Remember icon marks a generally interesting and useful fact — something you may want to remember for later use.
The Warning icon highlights lurking danger. When we use this icon, we’re telling you to pay attention and proceed with caution.
Where to Go from Here
You can start the book anywhere, but here are a couple of hints. If you’re brand-new to Python, start with Chapter 1. If you already have some Python experience and you want to learn how to work with bigger chunks of code, head to Chapter 8. For anything else, turn to the Table of Contents or the Index and you’ll find what you need.
Chapter 1
Starting with Python
IN THIS CHAPTER
Discovering why Python is hot
Finding the tools for success
Writing Python in VS Code
Because you’re reading this chapter, you probably realize that Python is a great language to know if you’re looking for a good job in programming, or if you want to expand your existing programming skills into exciting cutting-edge technologies such as artificial intelligence (AI), machine learning (ML), data science, or robotics, or even if you’re just building apps in general. So we’re not going to try to sell you on Python. It sells itself.
Our approach leans heavily toward the hands-on. A common failure in many programming tutorials is that they already assume you’re a professional programmer in some language, and they skip over things they assume you already know.
This book is different in that we don’t assume that you’re already programming in Python or some other language. We do assume that you can use a computer and understand basics such as files and folders.
We also assume you’re not up for settling down in an easy chair in front of the fireplace to read page after page of theoretical stuff about Python, like some kind of boring novel. You don’t have that much free time to kill. So we’re going to get right into it and focus on doing, hands-on, because that’s the only way most of us learn. We’ve never seen anyone read a book about Python and then sit at a computer and write Python like a pro. Human brains don’t work that way. We learn through practice and repetition, and that requires being hands-on.
Why Python Is Hot
We promised we weren’t going to spend a bunch of time trying to sell you on Python, and that’s not our intent here. But we would like to talk briefly about why it’s so hot.
Here are the main reasons cited for Python’s current popularity:
Python is relatively easy to learn.
Everything you need to learn (and do) in Python is free.
Python offers more ready-made tools for current hot technologies such as data science, machine learning, artificial intelligence, and robotics than most other languages.
Choosing the Right Python
There are different versions of Python out roaming the world, prompting many a beginner to wonder things such as
Why are there different versions?
How are they different?
Which one should I learn?
All good questions, and we’ll start with the first. A version is kind of like a car year. You can go out and buy a 1968 Ford Mustang, a 1990 Ford Mustang, a 2019 Ford Mustang, or a 2020 Ford Mustang. They’re all Ford Mustangs. The only difference is that the one with the highest year number is the most current Ford Mustang. That Mustang is different from the older models in that it has some improvements based on experience with earlier models, as well as features current with the times.
Programming languages (and most other software products) work the same way. But as a rule, we don’t ascribe year numbers to them because they’re not released on a yearly basis. They’re released whenever they’re released. The principle is the same, though. The version with the highest number is the newest, most recent model, sporting improvements based on experience with earlier versions, as well as features relevant to the current times.
In this book, we focus on versions of Python that are current in late 2023 from Python 3.11 and higher. Don’t worry about version differences after the first and second digits. Version 3.11.1 is similar enough to version 3.11.2 that version differences aren’t important, especially to a beginner. Most of what’s in Python is the same across all recent versions. So you need not worry about investing time in learning a version that is or will soon be obsolete.
Tools for Success
Now we need to start getting your computer set up so that you can learn, and do, Python hands-on. For one, you’ll need a good Python interpreter and editor. The editor lets you type the code, and the interpreter lets you run that code. When you run (or execute) code, you’re telling the computer to “do whatever my code tells you to do.”
The term code refers to anything written in a programming language to provide instructions to a computer. The term coding is often used to describe the act of writing code. A code editor is an app that lets you type code, in much the same way an app such as Microsoft Word or Apple Pages helps you type regular, plain-English text.
Just as there are many brands of toothpaste, soap, and shampoo in the world, there are many brands of code editors that work well with Python. There isn’t a right one or a wrong one, a good one or a bad one, a best one or a worst one. Just a lot of different products that basically do the same thing but vary slightly in their approach and what that editor’s creators think is good.
If you’ve already started learning Python and are happy with whatever you’ve been using, you’re welcome to continue using that and ignore our suggestions. If you’re just getting started with this stuff, we suggest you use VS Code, because it’s an excellent, free learning environment.
Installing Python and VS Code
The editor we recommend and will be using in this book is called Visual Studio Code, officially. But most often, it is spoken or written as VS Code. The main reasons why it’s our favorite follow:
It is an excellent editor for learning coding.
It is an excellent editor for writing code professionally and is used by millions of professional programmers and developers.
It’s relatively easy to learn and use.
It works pretty much the same on Windows, Mac, and Linux.
It’s free.
It integrates beautifully with GitHub Copilot, so you can use modern, generative AI to speed both learning and actual coding.
To use VS Code as your editor for learning and doing Python, you need to download and install Python, VS Code, and a VS Code extension. With luck, you already have some experience working with apps, so this won’t be difficult. You will have to follow onscreen instructions as you go along. If faced with any choices you’re not sure about along the way, you can just choose the default (suggested) option. Here are the steps to download and install Python and VS Code:
Use any web browser to browse to
www.python.org
.
Click Download and, if asked to select a version, choose the suggested stable version.
Open the folder to which you downloaded Python and double-click the icon for the file you downloaded to install Python.
You can just follow the onscreen instructions, and accept any suggested defaults, during the installation process.
Browse to
https://code.visualstudio.com/
and download the current version of VS Code for your operating system.
Open the folder to which you downloaded Visual Studio code, double-click the icon for the downloaded file, and follow the onscreen instructions to install VS Code.
After VS Code is installed, you should be able to start it like any other app in your system. In Windows, click Start and look around on the Start menu for Visual Studio Code icon. On a Mac, you should be able to find it in your Applications folder, or Launchpad.
Installing the Python extension
To use VS Code for Python coding, you need to install the VS Code Python extension for Python. When you open VS Code, you will see some icons listed down the left side of the window. Placing the mouse cursor over any icon reveals its name. Click the Extensions icon, shown in Figure 1-1, and then enter Python in the Search box at the top of the Extensions panel. Click the Install button with the Python extension from Microsoft (see Figure 1-1).
FIGURE 1-1: Obtaining the Python extension in VS Code.
When you’ve finished installing the Python extension, you might notice that both Python and Pylance were added as extensions to VS Code. Don’t worry; that’s normal. Pylance just gives you some additional capabilities that make it easier to learn and write Python code within the VS Code editor. To ensure that the extension is activated, exit VS Code and then restart it.
Letting AI write your Python code
Modern generative AI is perfectly capable of writing Python code for you. It’s not as simple as commanding it to “Write a Python app that will make me a billionaire,” however. It doesn’t work that way — yet. Unfortunately. You need to break things down into smaller chunks, and probably use accurate tech terminology, too. In other words, you still have to learn enough Python to be able to write your AI prompts accurately. Virtually all of these prompts — no matter which AI service you use — will start with “Write python code for …” because AI can do a lot of things. If you don’t tell it, specifically, that you want it to write Python code, you might get no code, HTML, JavaScript, or whatever. So just make sure you understand that, first and foremost.
As we write this in late 2023, generative AI is still fairly new and evolving rapidly. We can’t make any promises in terms of pricing or availability. Those things are likely to change often over the coming years, and competing businesses jockey for position and market share. But as of this writing, you can prompt the following AI services to write Python code:
ChatGPT (
https://chat.openai.com
)
Claude (
https://claude.ai
)
Google Bard (
https://bard.google.com
)
Microsoft Copilot (
https://copilot.microsoft.com
)
Most of these tools are free (right now), but again, we can’t make any promises about the future.
Using GitHub Copilot
GitHub Copilot is another AI tool that’s capable of writing code for you. It’s based on OpenAI’s GPT-4, like ChatGPT. However, it’s specifically geared toward working with code and integrates directly into VS Code. You’re certainly not required to use GitHub Copilot to learn Python or use this book, but you might find that it really helps your learning process. As we write this book, GitHub is offering Copilot for free to students. It offers some paid plans, too, starting at $10 a month. To use Copilot, you need to sign up for GitHub and purchase (or request) access to Copilot. Again, this tool is so new that any instructions we give here are subject to change. You may need to search Google or YouTube for use Copilot with VS Code to find the most up-to-date instructions. Basically, here’s how it works:
If you don’t already have a GitHub account, go tohttps://github.comand create an account.
Make sure you know your GitHub username and password, because you’ll need them to set up your account.
Open VS Code if it isn’t already open.
Click Extensions in the left column, and then enter Copilot in the Search box to search for Copilot.
A list of Copilot extensions appears.
Click the Install button at the right of the plain-old GitHub Copilot extension (not “Copilot Labs” or any of the others that appear), as shown in
Figure 1-2
.
FIGURE 1-2: The GitHub Copilot extension in VS Code.
You’ll see some instructions and tips on a pane to the right. You need not do anything with those right now, though. Near the lower-left corner of VS Code, you should see an avatar icon for Accounts (see Figure 1-3). Click that icon and choose Sign In with GitHub to Use GitHub Copilot. Follow the on-screen instructions to sign into your GitHub account and set up Copilot. But remember: Setting up a Copilot account isn’t a requirement, just an option. So don’t feel you have to complete the process of purchasing Copilot right now. But if you do add Copilot as an extension, you should see its name under Installed Extensions whenever you’re viewing extensions in VS Code.
Also, near the lower-right corner of the screen, you’ll see a tiny Copilot icon (also shown in Figure 1-3). You can click that icon at any time to deactivate Copilot if you feel it’s in your way while learning. Click it again to activate Copilot whenever you’re ready.
FIGURE 1-3: The Accounts and Copilot icons in VS Code.
The simple tasks you’ve completed in this chapter will serve you well through your learning process, as well as your professional programming after you’ve mastered the basics. Head on over to Chapter 2, and we’ll delve a bit deeper into Python and using the tools you now have available on your computer.
