Índice para Python Coding & Programming The Complete Manual em Python Coding & Programming The Complete Manual

Getting Started A Brief History of Coding It’s easy to think that programming a machine to automate a process, or calculate a value, is a modern concept that’s only really happened in the last fifty years or so. However, that assumption is quite wrong, coding has actually been around for quite some time. 01000011 01101111 01100100 01101001 01101110 01100111 Essentially all forms of coding are made up of ones and zeros - on or off states. This works for both a modern computer and even the oldest known computational device. ~87 BC It’s difficult to pinpoint an exact start of when humans began to ‘program’ a device. However, it’s widely accepted that the Antikythera Mechanism is possibly the first ‘coded’ artefact. It’s dated to about 87 BC and is an…

Getting Started Creating a Coding Platform The term ‘Coding Platform’ can denote a type of hardware, on which you can code, or a particular operating system, or even a custom environment that’s pre-built and designed to allow the easy creation of games. In truth it’s quite a loose term, as a Coding Platform can be a mixture of all these ingredients, it’s simply down to what programming language you intend to code in and what your end goals are. Coding can be one of those experiences that sounds fantastic, but to get going with it, is often confusing. After all, there’s a plethora of languages to choose from, numerous apps that will enable you to code in a specific, or range, of languages and an equally huge amount of third-party…

Hello, World Starting Python for the First Time The Raspberry Pi offers one of the best all-round solutions on which to learn and code, in particular, Python. Raspbian, the Pi’s recommended OS, come pre-installed with the latest stable version of Python 3, which makes it a superb coding platform. STARTING PYTHON Everything you need to begin programming with Python is available from the Raspberry Pi desktop. However, if you want, drop into the Terminal and update the system with: sudo apt-get update. STEP 1 With the Raspbian desktop loaded, click on the Menu button followed by Programming > Python 3 (IDLE). This opens the Python 3 Shell. Windows and Mac users can find the Python 3 IDLE Shell from within the Windows Start button menu and via Finder. STEP 2…

Hello, World Executing Code from the Command Line Although we’re working from the GUI IDLE throughout this book, it’s worth taking a look at Python’s command line handling. We already know there’s a command line version of Python but it’s also used to execute code. COMMAND THE CODE Using the code we created in the previous tutorial, the one we named hello.py, let’s see how you can run code that was made in the GUI at the command line level. STEP 1 Python, in Linux, comes with two possible ways of executing code via the command line. One of the ways is with Python 2, whilst the other uses the Python 3 libraries and so on. First though, drop into the command line or Terminal on your operating system. STEP…

Hello, World Working with Variables We’ve seen some examples of variables in our Python code already but it’s always worth going through the way they operate and how Python creates and assigns certain values to a variable. VARIOUS VARIABLES You’ll be working with the Python 3 IDLE Shell in this tutorial. If you haven’t already, open Python 3 or close down the previous IDLE Shell to clear up any old code. STEP 1 In some programming languages you’re required to use a dollar sign to denote a string, which is a variable made up of multiple characters, such as a name of a person. In Python this isn’t necessary. For example, in the Shell enter: name=”David Hayward” (or use your own name, unless you’re also called David Hayward). STEP 2…

Working with Data Opening Files In Python you can read text and binary files in your programs. You can also write to file, which is something we will look at next. Reading and writing to files enables you to output and store data from your programs. OPEN, READ AND WRITE In Python you create a file object, similar to creating a variable, only pass in the file using the open() function. Files are usually categorised as text or binary. STEP 1 Start by entering some text into your system’s text editor. The text editor is best, not a word processor, as word processors include background formatting and other elements. In our example, we have the poem The Cimmerian, by Robert E Howard. You need to save the file as poem.txt.…

Index Using Modules A Python module is a Python-created source file that contains the necessary code for classes, functions and global variables. You can bind and reference modules to extend functionality, and create even more spectacular Python programs. Are you curious about how to improve your use of these modules to add a little something extra to your code? Then read on and learn how they can be used to fashion fantastic code with graphics, animations and operating system specific commands.…

Using Modules Using the Math Module One of the most used modules you will come across is the Math module. As we’ve mentioned previously in this book, mathematics is the backbone of programming and there’s an incredible number of uses the Math module can have in your code. E = MC2 The Math module provides access to a plethora of mathematical functions, from simply displaying the value of Pi, to helping you create complex 3D shapes. STEP 1 The Math module is built-in to Python 3; so there’s no need to PIP install it. As with the other modules present, you can import the module’s function by simply entering import math into the Shell, or as part of your code in the Editor. STEP 2 Importing the Math module will…

Using Modules Python in Focus: Artificial Intelligence Artificial Intelligence (AI) and Machine Learning (ML) are the new hot topics of the IT industry. AI is fast becoming the working science fiction that it has been portrayed as in the past, and behind it is Python. Despite how close AI and ML are, there are distinct differences between the two technologies. AI refers to the study of how to train a computer to accomplice the things that humans can do significantly better and faster. Whereas, ML is the ability for a computer to learn from its experiences, so that the outcome and performance will eventually become more accurate and accomplished. While different, they are both essentially discussing the same element: training a system to learn and do things independently. Where AI…

Code Repository Number Guessing Game This is a simple little piece of code but it makes good use of the Random module, print and input, and a while loop. The number of guesses can be increased from 5 and the random number range can easily be altered too. NUMBERGUESS.PY Copy the code and see if you can beat the computer within five guesses. It’s an interesting bit of code that can be quite handy when your implementing a combination of the Random module alongside a while loop. 1 Although this is a reasonably easy to follow program, there are some elements to the code that are worth pointing out. To begin with, you need to import the Random module, as you’re using random numbers within the code. 2 This section…

Code Repository Playing Music with the Winsound Module Of course, instead of playing an existing MP3, you can always make your own music. The code below will play out Pachelbel’s Canon in D, no less. MUSIC.PY The code utilises both the Time and Winsound modules, defining the tone and pitch and inserting small pauses of .5 of a second. 1 The start of the code imports the Winsound and Tie modules; remember, this is a Windows-only Python script. The variable t is setting the duration, while p equals .5, which you can use for the time.sleep function. 2 These variables set the frequencies, with the corresponding numbers, which can be used in the next section of the code. 3 Winsound.beep requires a frequency and duration within the brackets. The frequencies…

Understanding Linux Creating and Deleting Files Being able to create and delete a file is an everyday computing skill. However, when using the Linux Terminal, there’s an element of care required, chiefly because any deleted files aren’t placed in the system recycle bin. CREATING FILES Once you learn to recognise the files and directories that make up Raspbian OS, it’s time to discover how to make your own. Knowing how to make, edit and delete files and directories is essential if you want to make your own projects. STEP 1 We’re going to create a file using a command called Touch. Touch is an interesting command that reaches out to a file, or directory, and updates it (this changes the system time as if you’d just opened the file). You…

Understanding Linux Useful System and Disk Commands Understanding these core Linux commands will enable you to not only master the inner workings of your Raspberry Pi but also to transfer those skills to other Linux distros, such as Ubuntu or Linux Mint. LOTS OF LINUX Linux is a huge and versatile command line language and there are hundreds of commands you can learn and use. Here are a few that can help you get more from your Raspberry Pi. STEP 1 The Raspberry Pi is a great little computer, so let’s start by getting some information. Enter: cat /proc/cpuinfo to view some details on your Raspberry Pi processors. If you have a Raspberry Pi 3 you will see four processors, along with the model name and other info. STEP 2…

Understanding Linux A-Z of Linux Commands There are literally thousands of Linux commands, so while this is not a complete A-Z, it does contain many of the commands you will most likely need. You will probably find that you end up using a smaller set of commands over and over again but having an overall knowledge is still very useful. A adduser Add a new user arch Print machine architecture awk Find and replace text within file(s) B bc An arbitrary precision calculator language C cat Concatenate files and print on the standard output chdir Change working directory chgrp Change the group ownership of files chroot Change root directory cksum Print CRC checksum and byte counts cmp Compare two files comm Compare two sorted files line by line cp Copy…

Getting Started What can You Do with Python? Python is an open-source, object-oriented programming language that’s simple to understand and write, yet also powerful and extremely malleable. It’s these characteristics that help make it such an important language to learn. Python’s ability to create highly readable code within a small set of instructions has a considerable impact on our modern digital world. From the ideal, first programmers’ choice to its ability to create interactive stories and games; from scientific applications to artificial Intelligence and web-based applications, the only limit to Python is the imagination of the person coding in it. It’s Python’s malleable design that makes it an ideal language for many different situations and roles. Even certain aspects of the coding world, that require more efficient code, still use…

Getting Started Python on the Pi If you’re considering on which platform to install and use Python, then give some thought to one of the best coding bases available: the Raspberry Pi. The Pi has many advantages for the coder: it’s cheap, easy to use, and extraordinarily flexible. THE POWER OF PI While having a far more powerful coding platform on which to write and test your code is ideal, it’s not often feasible. Most of us are unable to jump into a several hundred-pound investment when we’re starting off and this is where the Raspberry Pi can help out. While having a far more powerful coding platform on which to write and test your code is ideal, it’s not often feasible. Most of us are unable to jump into…

Index Hello, World Getting started with Python may seem a little daunting at first, but, thankfully, the language has been designed with simplicity in mind. Like most things, you need to start slow, master the basics, learn how to get a result, and how to get what you want from the code. This section covers numbers and expressions, user input, conditions and loops and the types of errors you will undoubtedly come across in your time with Python: the core foundations of good coding and Python code.…

Hello, World How to Set Up Python in Windows Windows users can easily install the latest version of Python via the main Python Downloads page. Whilst most seasoned Python developers may shun Windows as the platform of choice for building their code, it’s still an ideal starting point for beginners. INSTALLING PYTHON 3.X Microsoft Windows doesn’t come with Python preinstalled as standard, so it will be necessary to install it yourself manually. Thankfully, it’s an easy process to follow. STEP 1 Start by opening your web browser to www.python.org/downloads/. Look for the button detailing the Download link for Python 3.x. Python is regularly updated, changing the last digit for each bug fix and update. Therefore, don’t worry if you see Python 3.8, or more, as long as it’s Python 3,…

Hello, World Numbers and Expressions We’ve seen some basic mathematical expressions with Python, simple addition and the like. Let’s expand on that now and see just how powerful Python is as a calculator. You can work within the IDLE Shell or in the Editor, whichever you like. IT’S ALL MATHS, MAN You can get some really impressive results with the mathematical powers of Python; as with most, if not all, programming languages, maths is the driving force behind the code. STEP 1 Open up the GUI version of Python 3, as mentioned you can use either the Shell or the Editor. For the time being, you’re going to use the Shell just to warm our maths muscle, which we believe is a small gland located at the back of the…

Hello, World Python Modules We’ve mentioned modules previously, (the Math module) but as modules are such a large part of getting the most from Python, it’s worth dedicating a little more time to them. In this instance we’re using the Windows version of Python 3. MASTERING MODULES Think of modules as an extension that’s imported into your Python code to enhance and extend its capabilities. There are countless modules available and as we’ve seen, you can even make your own. STEP 1 Although good, the built-in functions within Python are limited. The use of modules, however, allows us to make more sophisticated programs. As you are aware, modules are Python scripts that are imported, such as import math. STEP 2 Some modules, especially on the Raspberry Pi, are included by…

Hello, World Python in Focus: Stitching Black Holes One of the biggest scientific, engineering and space-based projects came to a head in 2019, revealing humanity’s first glimpse at the universe’s most elusive object: a black hole. But what’s that got to do with Python? Imaging a black hole is pretty difficult. The very nature of a black hole means that nothing can escape its immense gravitational field, even light itself. To quote the Wikipedia entry for a black hole: “A black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from…

Using Modules Basic Animation Python’s modules make it relatively easy to create shapes, or display graphics and animate them accordingly. Animation though, can be a tricky element to get right in code. There are many different ways of achieving the same end result and we’ll show you one such example here. LIGHTS, CAMERA, ACTION The Tkinter module is an ideal starting point for learning animation within Python. Naturally, there are better custom modules out there, but Tkinter does the job well enough to get a grasp on what’s needed. STEP 1 Let’s make a bouncing ball animation. First, we will need to create a canvas (window) and the ball to animate: STEP 2 Save and Run the code. You will see a blank window appear, with a red ball sitting…

Index Code Repository We’ve included a vast Python code repository for you to freely use in your own programs. There’s plenty in here to help you create a superb piece of programming, or extend your project ideas. We’ve got code for making backups of your files and folders, number guessing games, random number generators, Google search code, game code, animation code, graphics code, text adventure code and even code that plays music stored on your computer. We’ve broken down some of the newer, and extended, concepts of the code to help you better understand what’s going on. This way you can easily adapt it to your own uses. This is an excellent resource that you won’t find in any other Python book. So use it, take it apart, adapt it…

Code Repository Random Number Generator User input and the ability to manipulate that input are important elements with any programming language. It’s what separates a good program from a great program, one that allows the user to interact and see the results of that interaction. RNDNUMGEN.PY It might be simple but this little piece of code will ask the user for two sets of numbers, a start and a finish. The code will then pluck out a random number between the two sets and display it. More Input While an easy code to follow, it could be more interesting if you prompt the user for more input. Perhaps you can provide them with addition, subtraction, multiplication elements with their numbers. If you’re feeling clever, see if you can pass the…

Code Repository Vertically Scrolling Text What’s not to like about vertically scrolling text? Its uses are many: the beginning of a game or introduction to something epic, like the beginning of every Star Wars movie; a list of credits at the end of something, such as a Python presentation. The list goes on. EPICSCROLL.PY We’ve used the poem Cimmeria by Robert E. Howard for the code’s scrolling text, along with a dramatic black background and red text. We think you’ll agree, it’s quite epic. A Long Time Ago… The obvious main point of enhancement is the actual text itself. Replace it with a list of credits, or an equally epic opening storyline to your Python game, and it will certainly hit the mark with whoever plays it. Don’t forget to…

Code Repository Text Adventure Script Text adventures are an excellent way to build your Python coding skills and have some fun at the same time. This example that we created will start you on the path to making a classic text adventure; where it will end is up to you. ADVENTURE.PY The Adventure game uses just the Time module to begin with, creating pauses between print functions. There’s a help system in place to expand upon, as well as the story itself. Adventure Time This, as you can see, is just the beginning of the adventure and takes up a fair few lines of code. When you expand it, and weave the story along, you’ll find that you can repeat certain instances such as a chance meeting with an enemy…

Code Repository Hangman Game Script Hangman is a great game to program into Python. It can be extremely complex, displaying graphics, the number of guesses left in the secret word, a huge bank of available words picked at random and countless other elements. It can also be quite simple. Here we have a mix between the two. HANGMAN.PY We’ve made a Hangman game board (the gallows) out of characters that can be displayed in the IDLE Shell, along with a huge bank of words to randomly choose from. QUIT() Since this is the last example in our Python code repository, we thought we’d go out with a bang and feature the hangman gallows being drawn with each incorrect guess of the word. Don’t worry if it looks misaligned in the…

Understanding Linux Using the Filesystem To master Linux, it’s important to understand how the filesystem works. What’s more, it’s also important to become familiar with the Terminal, or shell. This command line environment may appear daunting at first, but with practise, it soon becomes easy to use. GETTING AROUND To drop into the Terminal, click on the fourth icon from the left along the top of the Raspberry Pi desktop, the one with a rightfacing arrow and an underscore. This is the shell, or Terminal. STEP 1 First, you’re going to look at directories and the directory path. A directory is the same thing as a folder, however in Linux it’s always called a directory. These are placed inside each other using a “/” character. So when you see /…

Understanding Linux Create and Remove Directories Creating, moving and deleting directories aren’t as easy in the Terminal as they are within a desktop interface. You need to tell Linux to move the directories inside other directories, a process known as recursion. Sounds complex but you should quickly get the hang of it. MANAGING FILES AND DIRECTORIES Now that you know how to create files, you’ll want to learn how to make directories, which are the same thing as folders, as well as move items around. If you are more used to working with a desktop interface, this can take a bit of getting used to. STEP 1 Enter: ls to quickly view all the directories currently in in the home location. Directories are created using the “mkdir” command (make directory).…

Getting Started PYTHON in NUMBERS There’s a lot to like about Python, but don’t just take our word for it. Here are some amazing facts and figures surrounding one of the most popular programming languages of recent years. Python creator Guido Van Rossum named Python after reading scripts from Monty Python’s Flying Circus. Alexa, Amazon’s Virtual Personal Assistant, uses Python to help with speech recognition. As of the end of 2018, Python was the most discussed language on the Internet. PYTHON AND LINUX SKILLS ARE THE THIRD MOST POPULAR I.T. SKILLS IN THE UK. Data analysis and Machine Learning are the two most used Python examples. Disney Pixar uses Python in its Renderman software to operate between other graphics packages. OVER 75% OF RECOMMENDED CONTENT FROM NETFLIX IS GENERATED FROM…

Hello, World Equipment You Will Need You can learn Python with very little hardware or initial financial investment. You don’t need an incredibly powerful computer and any software that’s required is freely available. WHAT WE’RE USING Thankfully, Python is a multi-platform programming language available for Windows, macOS, Linux, Raspberry Pi and more. If you have one of those systems, then you can easily start using Python. □ COMPUTER Obviously you’re going to need a computer in order to learn how to program in Python and to test your code. You can use Windows (from XP onward) on either a 32 or 64-bit processor, an Apple Mac or Linux installed PC. □ AN IDE An IDE (Integrated Developer Environment) is used to enter and execute Python code. It enables you to…

Hello, World Saving and Executing Your Code While working in the IDLE Shell is perfectly fine for small code snippets, it’s not designed for entering longer program listings. In this section you’re going to be introduced to the IDLE Editor, where you will be working from now on. EDITING CODE You will eventually reach a point where you have to move on from inputting single lines of code into the Shell. Instead, the IDLE Editor will allow you to save and execute your Python code. STEP 1 First, open the Python IDLE Shell and when it’s up, click on File > New File. This will open a new window with Untitled as its name. This is the Python IDLE Editor and within it you can enter the code needed to…

Hello, World Creating Functions Now that you’ve mastered the use of variables and user input, the next step is to tackle functions. You’ve already used a few functions, such as the print command but Python enables you to define your own functions. FUNKY FUNCTIONS A function is a command that you enter into Python to do something. It’s a little piece of self-contained code that takes data, works on it and then returns the result. STEP 1 It’s not just data that a function works on. They can do all manner of useful things in Python, such as sort data, change items from one format to another and check the length or type of items. Basically, a function is a short word that’s followed by brackets. For example, len(), list()…

Hello, World Python Errors It goes without saying that you’ll eventually come across an error in your code, where Python declares it’s not able to continue due to something being missed out, wrong or simply unknown. Being able to identify these errors makes for a good programmer. DEBUGGING Errors in code are called bugs and are perfectly normal. They can often be easily rectified with a little patience. The important thing is to keep looking, experimenting and testing. Eventually your code will be bug free. STEP 1 Code isn’t as fluid as the written word, no matter how good the programming language is. Python is certainly easier than most languages but even it is prone to some annoying bugs. The most common are typos by the user and whilst easy…

Index Working with Data Data is everything; it can topple governments, change election results, and tell us the secrets of the universe. Over these coming pages we look at how you can create lists, tuples, dictionaries and multi-dimensional lists, and then how you can use them to forge exciting and useful programs. In addition, you will learn how you can use the date and time functions, write to files to your system and even create graphical user interfaces that will take your coding skills to new levels and into new project ideas.…

Working with Data Exceptions When coding, you’ll naturally come across some issues that are out of your control. Let’s assume you ask a user to divide two numbers and they try to divide by zero. This will create an error and break your code. EXCEPTIONAL OBJECTS Rather than stop the flow of your code, Python includes exception objects which handle unexpected errors in the code. You can combat errors by creating conditions where exceptions may occur. STEP 1 You can create an exception error by simply trying to divide a number by zero. This will report back with the ZeroDivisionError: Division by zero message, as seen in the screenshot. The ZeroDivisionError part is the exception class, of which there are many. STEP 2 Most exceptions are raised automatically when Python…

Working with Data Python in Focus: Gaming Although not always considered as the ideal programming language for developing games, Python has come a long way in recent years and is now one of the contributing elements to a huge number of titles. The video game industry generates something in the region of $140 billion each year, and that number is growing fast. It’s a long way from the 8-bit days of the Commodore 64 and ZX Spectrum; the arcade titles that used to devour our pocket money and the wood panelled home consoles that Atari lovingly developed. These days, it’s all about teams of coders, graphic artists, musicians, PR, projects and development platforms. GAME CODE Coding a game from scratch, using raw code, has become something of the past. Most…

Code Repository Python File Manager This file manager program displays a list of options that allow you to read a file, write to a file, append to a file, delete a file, list the contents of a directory and much more. It’s remarkably easy to edit and insert into your own code, or add to. 1 This part of the code imports the necessary modules. The OS and Subprocess modules deal with the operating system elements of the program. 2 Each def XXX() functions store the code for each of the menu’s options. Once the code within the function is complete, the code returns to the main menu for another option. 3 This is part of the code that checks to see what OS the user is running. In Windows…

Random Number Generator/Password Generator Random Password Generator We’re always being told that our passwords aren’t secure enough; well here’s a solution for you to implement into your own future programs. The random password generator code below will create a 12-letter string of words (both cases) and numbers each time it’s executed. RNDPASSWORD.PY Copy the code and run it; each time you’ll get a random string of characters that can easily be used as a secure password which will be very difficult for a password cracker to hack. Secure Passwords There’s plenty you can do to modify this code and improve it further. For one, you can increase the number of characters the generated password displays and perhaps you can include special characters too, such as signs and symbols. Then, you…

Code Repository Python Scrolling Ticker Script You may be surprised to hear that one of the snippets of code we’re often asked for is some form of scrolling ticker. Whilst we’ve covered various forms of scrolling text previously, the ticker is something that seems to keep cropping up. So, here it is. TICKER.PY We’re using Tkinter here along with the Time module to determine the speed the text is displayed across the window. Ticker Time The obvious improvements to the Ticker code lie in the speed of the text and what the text will display. Otherwise you can change the background colour of the ticker window, the font and the font colour, along with the geometry of the Tkinter window if you want to. Yet another interesting element that could…

Index Understanding Linux Linux is a remarkably versatile and powerful operating system. It’s used throughout the programming and engineering world, in science, space exploration, education, gaming and everything else in between. It’s the OS of choice for high-performance servers, it’s the backbone of the Internet and it powers the fastest supercomputers in the world. Knowing how to use Linux, and how it’s structured, is key to being able to create better Python content. The Raspberry Pi, for example, uses a Linux-based OS and, as such, makes for an excellent coding platform. Regardless of whether you’re using a Pi, like us, or a Linux Mint or Ubuntu, these pages will prove invaluable for your Python learning. Master Linux, master Python, and start engineering your coding future.…

Understanding Linux Listing and Moving Files Admittedly, using the desktop GUI to list and move files is much easier than using the Terminal and keyboard. However, it’s an important skill that you will appreciate as you advance with the Raspberry Pi and Linux. LOOKING AT FILES Operating systems are built on files and folders, or directories if you prefer. While you’re used to viewing your own files, most operating systems keep other files out of sight. In Raspbian, you have access to every file in the system. STEP 1 We’ve already looked at “ls”, which lists the files in the working directory, but you are more likely to use a command like “ls –l”. The bit after the command (the ‘-lah’) is known as the argument. This is an option…

Understanding Linux Copying, Moving and Renaming Files Taking command of the Terminal is essential when learning how your Raspberry Pi’s operating system works. The copying, moving and renaming of files is equally important, as you’ll be doing a lot of this throughout your Pi projects. USING THE MOVE COMMAND In Linux, renaming a file is simply moving it from one name to another and copying a file is moving it without deleting the original. Don’t panic, it’s quite easy to master. STEP 1 Before we can move anything around, we need to have a few test items in our home directory. Enter: touch testfile and mkdir testdir to create a test file and test directory in your home directory. Enter: ls to check that they are both present. STEP 2…

Understanding Linux Editing Text Files A text file in Linux can be anything from a simple set of instructions on how to use an app, to some complex Python, C++ or other programming language code. Text files can be used for scripting, automated executable files, as well as configuration files too. THE JOY OF TEXT To be able to edit or create a text file, you need a good text editor. Linux has many but here are some in action on the Raspberry Pi. STEP 1 The first text editor for the Raspberry Pi is the default desktop environment app: Leafpad. To use, you can either double-click an existing text file or click the Raspberry Pi menu icon (in the top left of the desktop) and from the Accessories menu,…