Python 3编程实践：艰难之路

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"Learn Python 3 the Hard Way" 是一本针对初学者的Python编程教程，旨在通过实践的方式帮助读者深入理解和掌握Python 3语言。本书采用了一种所谓的“笨办法”，即通过大量的练习和实际编码来教授编程基础，强调动手实践的重要性。在Python 3版本中，学习者将接触并学习到以下关键知识点： 1. **基础语法**：包括变量声明、数据类型（如整型、浮点型、字符串和布尔型）、输入/输出操作、基本算术运算和比较运算符。 2. **控制流**：学习如何使用条件语句（if-else）进行逻辑判断，以及循环结构（for和while）进行重复执行。 3. **函数**：了解如何定义和调用函数，传递参数，以及返回值的概念。 4. **列表与元组**：掌握这两种序列数据类型的使用，包括元素的添加、删除、索引访问和切片操作。 5. **字典与集合**：学习这两种映射数据类型，理解它们的特点和应用场景。 6. **字符串操作**：学习字符串的拼接、查找、替换、分割等方法，以及格式化输出。 7. **文件操作**：学会读写文件，理解文件对象和缓冲区的概念。 8. **异常处理**：了解如何使用try-except语句处理程序中的错误和异常。 9. **模块与包**：理解Python的模块化编程，学会导入和使用标准库及第三方库。 10. **面向对象编程**：介绍类和对象的概念，学习创建类、实例化对象，以及继承、封装和多态性。 11. **函数式编程**：了解高阶函数、闭包、装饰器等函数式编程特性。 12. **调试与测试**：学习如何使用调试工具找出代码中的错误，以及编写测试用例确保代码的正确性。本书通过EPUB格式提供电子版，这是一种开放的电子书标准，支持在多种阅读设备和应用程序上使用。读者可以根据自己的喜好调整字体、字号、单双列布局、横竖屏模式，以及点击或触摸图像以放大查看。对于包含编程代码或配置示例的部分，为了优化显示效果，建议在单列、横屏模式下，并将字体调至最小，以便更清晰地查看代码。在某些情况下，当可流动格式可能影响代码的呈现时，会提供一个“点击此处查看代码图片”的链接，点击后可以查看与印刷版书籍类似格式的代码图片。通过本书的学习，读者将能够逐步建立起坚实的Python编程基础，为进一步深入学习和应用Python打下坚实的基础。

Introduction: Shut Up and Shell
How to Use This Appendix
You Will Be Memorizing Things
The Setup
Do This
You Learned This
Do More
Paths, Folders, Directories (pwd)
Do This
You Learned This
Do More
If You Get Lost
Do This
You Learned This
Make a Directory (mkdir)
Do This
You Learned This
Do More
Change Directory (cd)
Do This
You Learned This
Do More
List Directory (ls)
Do This
You Learned This
Do More
Remove Directory (rmdir)
Do This
You Learned This
Do More
Moving Around (pushd, popd)
Do This
You Learned This
Do More
Making Empty Files (touch/New-Item)
Do This

Preface

This simple book is meant to get you started in programming. The title says it’s the hard way to learn

to write code, but it’s actually not. It’s only the “hard” way because it uses a technique called

instruction. Instruction is where I tell you to do a sequence of controlled exercises designed to build

a skill through repetition. This technique works very well with beginners who know nothing and need

to acquire basic skills before they can understand more complex topics. It’s used in everything from

martial arts to music to even basic math and reading skills.

This book instructs you in Python by slowly building and establishing skills through techniques such

as practice and memorization, then applying them to increasingly difficult problems. By the end of the

book you will have the tools needed to begin learning more complex programming topics. I like to tell

people that my book gives you your “programming black belt.” What this means is that you know the

basics well enough to now start learning programming.

If you work hard, take your time, and build these skills, you will learn to code.

Improvements in the Python 3 Edition

Learn Python 3 the Hard Way now uses Python 3.6. I’ve standardized on this version of Python

because it has a new, improved string formatting system that is easier to use than the previous 4 (or 3,

I forget, there were many) versions. There are a few problems with Python 3.6 for beginners, but I

help you navigate these issues in the book. A particularly hairy problem is that Python 3.6 has very

poor error messages in some key areas that I help you understand.

I have also improved the videos based on my experiences over the last five years teaching people

Python. You can watch these videos online at informit.com/title/9780134692883. In the past the

videos simply let you watch me do the exercise. The Python 3 edition videos also show you how to

break—and then fix—every exercise. This skill is called “debugging.” It teaches you how to fix

problems you run into but also how Python runs the programs you’re creating. The goal of this new

methodology is to build a mental model of how Python runs your code so you can more easily figure

out why it’s broken. You’ll also learn many useful tricks for debugging broken software.

Last, the Python 3 edition fully supports Microsoft Windows 10 from beginning to end. The previous

edition focused mostly on the Unix-style systems such as macOS and Linux, with Windows being

more of an afterthought. At the time I started writing the Python 3 edition Microsoft had started to take

open source tools and developers seriously, and it was difficult to ignore them as a serious Python

development platform. The videos feature Microsoft Windows using Python in various scenarios and

also show macOS and Linux for full compatibility. I tell you about any gotchas on each platform,

cover installation instructions, and provide any other tips I can give you.

The Hard Way Is Easier

With the help of this book, you will do the incredibly simple things that all programmers do to learn a

programming language:

1. Go through each exercise.

2. Type in each file exactly.

3. Make it run.

That’s it. This will be very difficult at first, but stick with it. If you go through this book and do each

exercise for one or two hours a night, you will have a good foundation for moving on to another book

about Python to continue your studies. This book won’t turn you into a programmer overnight, but it

will get you started on the path to learning how to code.

This book’s job is to teach you the three most essential skills that a beginning programmer needs to

know: reading and writing, attention to detail, and spotting differences.

Reading and Writing

If you have a problem typing, you will have a problem learning to code, especially if you have a

problem typing the fairly odd characters in source code. Without this simple skill you will be unable

to learn even the most basic things about how software works.

Typing the code samples and getting them to run will help you learn the names of the symbols, get

familiar with typing them, and get you reading the language.

Attention to Detail

The one skill that separates good programmers from bad programmers is attention to detail. In fact,

it’s what separates the good from the bad in any profession. You must pay attention to the tiniest

details of your work or you will miss important elements of what you create. In programming, this is

how you end up with bugs and difficult-to-use systems.

By going through this book, and copying each example exactly, you will be training your brain to

focus on the details of what you are doing, as you are doing it.

Spotting Differences

A very important skill (that most programmers develop over time) is the ability to visually notice

differences between things. An experienced programmer can take two pieces of code that are slightly

different and immediately start pointing out the differences. Programmers have invented tools to make

this even easier, but we won’t be using any of these. You first have to train your brain the hard way,

then use the tools.

While you do these exercises, typing each one in, you will make mistakes. It’s inevitable; even

seasoned programmers would make a few. Your job is to compare what you have written to what’s

required and fix all the differences. By doing so, you will train yourself to notice mistakes, bugs, and

other problems.

Ask, Don’t Stare

If you write code, you will write bugs. A “bug” means a defect, error, or problem with the code

you’ve written. The legends say that this comes from an actual moth that flew into one of the first

computers causing it to malfunction. Fixing it required “de-bugging” the computer. In the world of

software, there are a lot of bugs. So many.

Like that first moth, your bugs will be hidden somewhere in the code, and you have to go find them.

You can’t just sit at your computer screen staring at the words you’ve written hoping that the answer

jumps out at you. There is no more additional information you can get doing that, and you need

additional information. You need to get up and go find the moth.

To do that you have to interrogate your code and ask it what is going on or look at the problem from a

different view. In this book I frequently tell you to “stop staring and ask.” I show you how to make

your code tell you everything it can about what’s going on and how to turn this into possible solutions.

I also show you how to see your code in different ways, so you can get more information and insight.

Do Not Copy-Paste

You must type each of these exercises in, manually. If you copy-paste, you might as well not even do

them. The point of these exercises is to train your hands, your brain, and your mind in how to read,

write, and see code. If you copy-paste, you are cheating yourself out of the effectiveness of the

lessons.

Using the Included Videos

Learn Python 3 the Hard Way has an extensive set of videos demonstrating how the code works and,

most importantly, how to break it. The videos are the perfect place to demonstrate many common

errors by breaking the Python code on purpose and showing you how to fix it. I also walk through the

code using debugging and interrogation tricks and techniques. The videos are where I show you how

to “stop staring and ask” the code what’s wrong. You can watch these videos online at

informit.com/title/9780134692883.

A Note on Practice and Persistence

While you are studying programming, I’m studying how to play guitar. I practice it every day for at

least two hours a day. I play scales, chords, and arpeggios for an hour and then learn music theory, ear

training, songs, and anything else I can. Some days I study guitar and music for eight hours because I

feel like it and it’s fun. To me repetitive practice is natural and just how to learn something. I know

that to get good at anything I have to practice every day, even if I suck that day (which is often) or it’s

difficult. Keep trying, and eventually it’ll be easier and fun.

Between the time that I wrote Learn Python the Hard Way and Learn Ruby the Hard Way I

discovered drawing and painting. I fell in love with making visual art at the age of 39 and have been

spending every day studying it in much the same way that I studied guitar, music, and programming. I

collected books of instructional material, did what the books said, painted every day, and focused on

enjoying the process of learning. I am by no means an “artist,” or even that good, but I can now say

that I can draw and paint. The same method I’m teaching you in this book applied to my adventures in

art. If you break the problem down into small exercises and lessons, and do them every day, you can

learn to do almost anything. If you focus on slowly improving and enjoying the learning process, then

you will benefit no matter how good you are at it.

As you study this book, and continue with programming, remember that anything worth doing is

difficult at first. Maybe you are the kind of person who is afraid of failure, so you give up at the first

sign of difficulty. Maybe you never learned self-discipline, so you can’t do anything that’s “boring.”

Maybe you were told that you are “gifted,” so you never attempt anything that might make you seem

stupid or not a prodigy. Maybe you are competitive and unfairly compare yourself to someone like me

who’s been programming for more than 20 years.

Whatever your reason for wanting to quit, keep at it. Force yourself. If you run into a Study Drill you

can’t do, or a lesson you just do not understand, then skip it and come back to it later. Just keep going

because with programming there’s this very odd thing that happens. At first, you will not understand

anything. It’ll be weird, just like with learning any human language. You will struggle with words and

not know what symbols are what, and it’ll all be very confusing. Then, one day, BANG—your brain

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Python 3编程实践：艰难之路

Python3编程：艰难之路

掌握Python编程：从Learn Python The Hard Way起步

Python 3编程硬路学习：基础入门

Learn Python 3 the hard way

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LEARN PYTHON 3 THE HARD WAY

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