Kitobni o'qish: «Python Handbook For Beginners»

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INTRODUCTION

1 How To Work With This Book?

This book suggests 11 themes that, once mastered, will give you basic skills in Python programming. These themes are arranged according to their difficulty level, from simple to more complex. If you wish to skip chapters, you are welcome to do so but bear in mind that every chapter contains concepts given in preceding chapters.

To get the most of this book, I highly recommend creating your version of every code given in the book. Tweak the code and see how it affects the output of the program.

It is also highly recommended that you take every test given at the end of chapters. Should you stack anywhere, you can always refer to the test answers given at the end of the book. But don't go there too soon. Take your time and reattend past topics.

Finally, it's worth mentioning that you don't need to install any software to write and run your code as you navigate through the book. You can use the free Python compiler (a program to write and run code), available here: https://online.qiber.org/code. No need to register or log in. I will be using this compiler in the book, and you may feel free to do the same. Should you decide to use other Python compilers, go ahead! There are many excellent, free compilers on the web. Here are some of them:

https://www.programiz.com/python-programming/online-compiler/

https://www.onlinegdb.com/online_python_interpreter

https://www.w3schools.com/python/trypython.asp?filename=demo_compiler

I am not affiliated with the above compilers and don't take any credits for them. I just want to give you some help diving into practical coding as soon as possible.

2 Why Python?

Python is one of the easiest to learn, yet, one of the most popular and widely used programming languages.

I would recommend Python as the first programing language to anyone who wants to learn to code. Why?

Python has a clean, minimalistic syntaxis. That almost looks like a natural language, which makes it easy to write and read the code.

It can take just a few lines of Python code to write a small script that does something. Simultaneously, it would require dozens of code lines in Java or C++, for instance, to complete the same piece of code.

Python is a high-level programing language, which means that it automates many essential tasks, such as memory management, which helps you focus on the core functionality of the program you create.

Python is extremely popular in the real world. Think of Google, Instagram, Netflix. They all use Python in areas that involve machine learning, data structuring, and processing.

Python is truly universal. Not only it works excellent for data-related scientific tasks. But you can build web apps and games too. Thanks to the respective Python frameworks.

Lastly, Python has a loyal and ever-growing community of supporters. Meaning the scale for Python application and the level of quality and efficiency of software built with Python will only grow.

3 Brief History

In 1980, Guido van Rossum, a fellow at the Dutch CWI, set out to develop a powerful yet easy-to-read programming language.

Guido was developing Python in his spare time for one of the projects that required a scripting language.

While working on it, Guido borrowed some groundwork from another programming language that he was also developing. It was ABC language, created to teach programming.

Today Python is a popular, versatile, and mature programming language with many rich application libraries and extensions.

Professional programmers use it for various fascinating projects and support the language as a part of the global Python community.

Although professionals use Python, it is ideal for beginners. It helps schoolchildren, students, and simply novice developers take their first steps into the world of programming.

By the way, Guido named it so not in honor of the well-known snake species but the once-popular comedy TV show "Monty Python's Flying Circus." However, the language is still associated with the snake, reflecting snakes heads on its logo.

4 What Can You Create With Python?

Today, Python is used in various applications, including social media, artificial intelligence, and games like Civilization, Battlefield, World of Tanks, etc. Let's take a closer look at the examples.

Social Media

Billions of people use services like Facebook, Instagram, Reddit, Pinterest, and Quora. All of the mentioned services implement Python and its powerful features for data processing.

Search Engines

Major search engines like Google, Yahoo!, Yandex, Mail.ru use Python in their products for the same reason as mentioned above. Python is very efficient for data processing and management. It's also a dominating programming language for artificial intelligence algorithms that comprise a considerable part of search engine services.

Video Games

Popular video games like Civilization, Battlefield, and World of Tanks use this Python in their architecture. Its application is growing in game development due to the constant improvement and release of specific Python game dev frameworks and libraries.

Streaming and Cloud Storage

Youtube, Netflix, Spotify, and Dropbox use Python. Worth mentioning that Guido van Rossum has been working in the Dropbox company from 2013 until his official retirement in 2019.

Space And Neural Network

NASA uses Python in their Workflow Automation Systems, while SpaceX uses Python for testing.

Tesla uses Python too. Its developers build Autopilot neural network initially in Python for rapid iteration; Python's syntaxis is clean and minimalistic. It allows building and testing functional prototypes fast.

CHAPTER ONE: LET’S GET CODING!

1 Your First Line Of Code

Any, even the most advanced python program, starts with the first line of code. Here is an example of a simple program that has just one line of code. The only thing the program does is it outputs the message: "Hey! This is my first line of code!"

Open the console and write the following:

print("Hey! This is my first line of code!")

Don't worry. We'll learn what this code means in the following chapters. Now it's essential to get you going! When done, run the code by hitting the green play button. Here is the result you should get:

Well done! You've just started and have already written your first simple program.

2 What Is a Program?

Even if it was just a single line of code, we've created a program. Like those that make computers work.

But what is a program? A program is a set of instructions and rules for a computer written in a programming language. If that makes sense, let's go on and reinforce what we have learned. Here is the code I've shuffled. It will help if you put it so that it would make it work.

"Once upon a time…!" () print

If you put it right, you should get a program that prints a sentence. Here it is below.

Are you done with the task? Great! In both programs that we have just created, we used a print function. We will use it a lot in this book. But first, let's dive a little deeper into it.

3 Print Function

Print is the function that does what it's called: it "prints" text on a screen. Programmers use this function to show messages to users. Such as "Your session is expired, please log in" or "Your password is too weak, please use a stronger password," etc.

Not only simple text messages, but the print function can also display different calculation results, presented in numeric format. We will learn all this stuff in the coming chapters. For now, we will focus purely on the print function and code some more with it.

Here is the plain text for you. Please use it with the print function, so when you run the code, it shows you the following message: Hey! I keep coding! Here is what you should get:

Have some fun. Since now you have learned how to write a program that displays messages, experiment with different messages you want your program to print. Use numbers too. Try adding or removing anything from your code. And then watch what happens; This is the best way to learn how the code operates.

4 How Does Python Read The Code?

As soon as you run the code, the computer starts reading it line by line, from top to button. Just like you're reading this book or anything. It may not sound too important, but it's essential to consider it when building and arranging our code; This is why some elements like modules (we will learn them in the following chapters) belong at the top of the code. We import them first to use them further down.

5 Counting Program

Let's build a program that counts from 1 to 3. Here is the code we need to do that:

print("1")

print("2")

print("3")

Pretty simple, right? Now extend the code so that it could count to 10. Here is the result you should get when you run your extended program:

6 Python Challenge

Let's celebrate the completion of the first chapter with a small challenge. You need to complete the below line of code so that it could output the message: "I nailed the first chapter!"

Here is what the output should look like when you fix and run the program:

7 Wrapping Up Chapter One

In the first chapter, we have accomplished the following:

1) Learned what Python is;

2) Understood what a program is;

3) Found out how does Python read the code;

4) Wrote our first line of code;

5) Created a few simple programs;

6) Finally, we learned and applied the print function.

8 Chapter One Test

1. A computer program is a:

1) Set of instructions and rules for a computer, written in a programming language.

2) Piece of code written on a computer.

3) Downloadable game.

2. How do we let a computer know that it needs to display a message on the screen?

1) With a magic word.

2) Using the print() function)

3) Using the command "Display message!"

3. In what order does a computer process (read) the code?

1) When we run the code, the computer reads that code line by line. Top-down.

2) When we run the code, the computer reads that code from bottom to top.

3) When we run the code, the computer doesn't read anything; it remembers everything by heart.

4. Arrange the parts of the code so that the program displays the message "I love Python!"

)

(

"I love Python!"

CHAPTER TWO: VARIABLES

1 What is a Variable?

A variable is a simple data structure that has a name and a value. Now, let's figure out what is what.

Imagine a folder on your desktop. In this case, the folder is a variable. The folder has the label "film."; This is the name of the variable. The folder contains a video called "The."; This is the value of the variable.

Here is how this variable looks in Python language:

Let's break it down.

1) First, we give a name to our variable – film

2) Second, we put equal sign =

3) Third, we give a value to our variable "Super Cat."

A value in a variable always goes with quotes, like in our example. Otherwise, a variable will not work.

Now, as we know what a variable is and what it contains, let's make one!

2 How to Create a Variable?

Write our variable from the example above to the console:

film = "Super Cat"

And run the code. Nothing? That's right. There is no message to show on the screen as we did not use the print function. We will combine variables with print function in the following chapters. But, for now, hit the >_REPL button.

You should now see the input field that looks like this:

Input the name of our variable, which is the film, and hit enter.

In response to the variable name, the program returns its value, which in our case is "Super Cat."

Now, as you've created your first variable, experiment with it. Change name and value. See what happens.

3 Let's Print Variable Value

We've just learned how to create a variable. Now let's learn how to output its value.

Do you remember the print function we used earlier? Let's combine it with our variable and see what happens. Write this code in the console and hit run:

film = "Super Cat"

print(film)

Let's break it down:

1) First, we declared a variable and gave it a name – film.

2) Then we assigned a value to the variable – Super Cat.

3) Then, on a second line, we wrote a print function.

And finally, we passed the variable name to the print function, putting it in the function brackets.

Every time we create a variable and pass its name to the print function, it will output the variable's value, just like in our example.

Now you know how programmers display variables in Python. It doesn't seem too tricky. Let's have some practice. Below is the code that is missing some elements. You have to fix it so the program could create a variable and display its value.

= " "

()

By now, you should have sufficient knowledge and skills to accomplish this task. When done, iterate on it as long as you like. Change variable names and values. Hone on your new skills!