Python Coding & Programming The Complete Manual -julkaisun Issue 3 -irtonumeron sisällysluettelo

01000011 01101111 01100100 01100101 Essentially all forms of coding are made up of ones and zeros, on or off states. This works for 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 ancient Greek analogue computer and orrery used to predict astronomical positions. ~850 AD The Banū Mūsā brothers, three Persian scholars who worked in the House of Wisdom in Baghdad, published the Book of Ingenious Devices in around 850 AD. Among the inventions listed was a mechanical musical instrument: a hydro-powered organ that played interchangeable cylinders automatically. 1800…

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 it’s 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 Python. For example, NASA utilises Python both as a stand-alone language and as a bridge between other programming languages. This way, NASA scientists and engineers are able to get to the data they need without having to cross multiple language…

Now that you have the latest version of Python installed, you can begin to get programming. These are your first steps in the wider world of Python and we’re here to help you write your first piece of code, save it, and run it in the Python IDLE Shell. We cover variables, numbers and expressions, user input, conditions and loops, and the types of errors you will undoubtedly come across in your time with Python. Let’s start and see how to get coding.…

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. 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 you need to create your future programs. STEP 2 The IDLE Editor is, for all intents and purposes, a simple text editor with Python features, colour coding and so on. You enter code as you would within the Shell, so taking an example from the previous tutorial, enter: STEP 3 As…

FUNKY FUNCTIONS A function is a command that you enter into Python in order 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 only data that a function works on. Functions 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 followed by brackets. For example, len(), list(), or type(). STEP 2 A function takes data, usually a variable, works on it depending on what the function is programmed to do, and returns the end value. The data being worked on goes inside the brackets, so if you wanted…

DEBUGGING Errors in code are called bugs, they’re perfectly normal and can often be easily rectified with a little patience. The import 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 while easy to find in simple dozen-line code, imagine having to debug multi-thousand line code. STEP 2 As we’ve mentioned, the most common of errors is the typo, often at the command level, mistyping the print command for example. However, they also occur when you’ve got numerous variables, all of…

OPEN, READ AND WRITE In Python, you create a file object, similar to creating a variable, only you 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 preferable to 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, and we’ve saved the file as poem.txt. STEP 2 You use the open() function to pass the file into a variable as an object. You can name the file object anything you like, but you will need to tell Python the name and location of the text file you’re opening: The reason for…

GOING GRAPHICAL You can draw simple graphics, lines, squares and so on, or you can use one of the many Python modules available to bring out some spectacular effects. STEP 1 One of the best graphical modules to begin learning Python graphics is Turtle. The Turtle module is, as the name suggests, based on the turtle robots used in many schools that can be programmed to draw something on a large piece of paper on the floor. The Turtle module can be imported with: import turtle. STEP 2 Let’s begin by drawing a simple circle. Start a New File, then enter the following code: As usual press F5 to save the code and execute it. This will open up a new window and the ‘Turtle’ will draw a circle. STEP…

FREE AND OPEN Linux is a fantastic fit for those who want something different. The efficiency of the system, the availability of applications, and its stability are just a few reasons why it’s a great Python coding resource. The first thing we need to address is that there is no such operating system called Linux. Linux is, in fact, the operating system kernel, the core component of an OS. When talking about Linux, what we, and others, are referring to is one of the many distributions, or distros, that use the Linux kernel. No doubt you’ve heard of at least one of the current popular distros: Ubuntu, Linux Mint, Fedora, openSUSE, Debian, Raspbian… the list goes on. Each one of these distros offers the user something a little different. While…

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 can see Touch in access using “ls –l” and checking the time next to a directory (such as Scratch). STEP 2 Now enter: touch Scratch and ls –l again and notice that the time has changed. It now matches the current time. You…

We’ve included a unique Python code repository for you to freely use in your own programs. There’s everything you can think of in here to help you create a superb piece of programming. We’ve got code that covers 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. This is an excellent resource that you won’t find in any other Python book. So use it, take it apart, adapt it to your own programs, and see what you can create. Check out PCL's Code Portal 50 FREE Complete Programs! Over 20,000 lines of code! Visit: pclpublications.com/exclusives Please note: Sign up is required to download…

POLYGONCIRCLES.PY There’s lots of mathematics used here along with some intricate coordinate manipulation with the Turtle module. Enter the code and execute it to see how it turns out. Graphical Enhancements There are several ways in which you can improve this code to make it more interesting. You can insert colours, perhaps a different colour for every line. You can display a message inside the circle and have the Turtle draw around it. Let your imagination run wild on this one. Turtle’s graphics can take a while to map out and draw, depending on how big and how intricate an image it is you’re designing. Whilst the effect can be quite stunning, it is limited by the amount of time it takes to display an image. Therefore it’s worth seeing…

TXT2BIN.PY Naturally we’re using the format function to convert the user’s entered text string into its binary equivalent. If you want to check its accuracy, you can plug the binary into an online convertor. 1000010 1101001 1101110 1100001 1110010 1111001 The text to binary convertor does offer some room for improvement and enhancement. There are many uses: it could be utilised in a password or secret word script, as part of an adventure game or just a novel way to display someone’s name. With regards to improvements, you could display the binary conversion in a Pygame window, using the animated text options from page 100. You could also ask the user if they wanted to have another go, or even ask if they wanted the binary output to be saved…

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 be introduced is one of the many text to Speech modules available for Python 3. You could pip install one, import it, then as the ticker displays the text, the text to speech function will read out the variable at the same time, since the entire text is stored in the variable labelled ‘s’. The ticker example can be used for system warnings, perhaps something that will display across your work or home…

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 text here, this is merely due to the differences between using the Python IDLE editor and pasting the code into a word processor (which formats things differently). There’s plenty you can do to improve, enhance and expand on what we’ve presented here. You can include a routine that returns an error if the user enters a number…

SQL SQL stands for Structured Query Language. SQL is a standard language for accessing and manipulating databases. Although SQL is an ANSI (American National Standards Institute) standard, there are different versions of the SQL language. However, to be compliant, they all support at least the major commands such as Select, Update and Delete in a similar manner. JAVASCRIPT JavaScript (often shortened to JS) is a lightweight, interpreted, object-oriented language with first class functions. JavaScript runs on the client side of the web, that can be used to design or program how the web pages behave on the occurrence of an event. JavaScript is an easy to learn and also powerful scripting language, widely used for controlling web page behaviour. JAVA Java is the foundation for virtually every type of networked…

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 2022, 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 MACHINE LEARNING – CODED BY PYTHON. 90% OF ALL FACEBOOK POSTS ARE FILTERED THROUGH PYTHON-CODED MACHINE LEARNING. IT’S ESTIMATED THAT OVER 75% OF NASA’S WORKFLOW AUTOMATION SYSTEMS ON-BOARD THE I.S.S. USE PYTHON. 16,000 There are over 16,000 Python…

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 a several hundred-pound investment when we’re starting off and this is where the Raspberry Pi can help out. The Raspberry Pi is a fantastic piece of modern hardware that has created, or rather re-created, the fascination we once all had about computers, how they work, how to code…

STARTING PYTHON As when learning anything new, you need to start slow. You can pick up the pace as your experience grows, but for now, let’s just get something appearing on the screen. Don’t worry, you’ll soon be coding like a pro! STEP 1 Click on the Windows Start button, and start typing ‘idle’. The result will be the currently installed version of Python, IDLE (Python 3.7 32-bit), for example. You can Pin it to the Start for convenience, otherwise simply click the icon to launch the Python Shell. STEP 2 The Shell is where you can enter code and see the responses and output of code you’ve programmed into Python. This is a kind of sandbox, if you will, where you’re able to try out some simple code and…

COMMAND THE CODE Using the code we created in the previous tutorial, the one we named hello.py, let’s see how we can run code that was made in the GUI at the command line level. STEP 1 When you first installed Python, the installation routine automatically included all the necessary components to allow the execution of code outside of the GUI IDLE; in other words, the command line. To begin with, click on the Windows Start Button, and type: cmd. STEP 2 As you did when launching the Python IDLE, click on the returned result from the search, the Command Prompt App. This will launch a new window, with a black background and white text. This is the command line, also called a Terminal in macOS, Linux, and Raspberry Pi…

VARIOUS VARIABLES We’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, so, for example, in the Shell enter: name=”David Hayward” (use your own name, unless you’re also called David Hayward). STEP 2 You can check the type of variable in use by issuing the type () command, placing the name of the variable inside the brackets. In our example, this would be: type (name). Add a new string variable:…

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, as such, will give you access to the module’s code. From there, you can call up any of the available functions within Math, by using math, followed by the name of the function in question. For example, enter: This will display the sine of 2. STEP 3 As you…

Linux is a flexible and powerful operating system but it also has a unique filesystem and way of doing things. Therefore, learning how Linux works is essential to creating better Python code. You’ll find that Linux already has Python elements built-in and if you’re working on a Raspberry Pi 4, then everything you need to code with Python is ready from the start. In this section we will mainly focus on using the Raspberry hardware with Linux but regardless of whether you’re using an RPi, Linux Mint, or Ubuntu, these pages will prove invaluable for your Python learning.…

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 / home/pi it means the pi directory is inside the home directory. Enter: clear and press return to clean the screen. Now enter: pwd. This stands for Print Working Directory and displays /home/pi.. STEP 2 When you log in to your Raspberry Pi, you don’t start at the…

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). Enter: mkdir testdir to create a new directory in your home directory. Enter: ls again to see it. STEP 2 The “mkdir” command is different to touch, in that it doesn’t update the timestamp if you use it with a directory that already exists. Enter: mkdir testdir again and you’ll get the…

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, choose Text Editor. STEP 2 From the Terminal there are even more options, although using the correct command, you can launch any of the desktop apps via the Terminal. One of the simplest, and a classic text editor that’s carried over from the Unix days, is vi. In the Terminal, enter:…

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 Remember that cat is used to list the contents of a text file, which is what cpuinfo is. There are other text files with system info available. Try “cat / proc/meminfo” to get information about your memory, “cat / proc/partitions” for information…

TERMINAL FUN All these commands are Linux-based, so not only can you use them on the Raspberry Pi but also on any of the Debian-based Linux distributions. STEP 1 The first command we’re going to use is sl, it’s not installed by default so enter: sudo apt-get install sl. The command can be run with sl and when executed displays a Steam Locomotive travelling across the screen (hence ‘sl’). Entering: LS (note the upper case) also works. STEP 2 Fans of Star Wars even get a fix when it comes to the Terminal. By linking to a remote server via the telnet command, you can watch Episode IV: A New Hope being played out, albeit in ASCII. To view this spectacle, enter: sudo apt-get install telnet, followed by: telnet towel.blinkenlights.nl…

TOP 10 COMMANDS These may not be the most common commands used by everyone but they will certainly feature frequently for many users of Linux and the command line. cd The cd command is one of the commands you will use the most at the command line in Linux. It allows you to change your working directory. You use it to move around within the hierarchy of your file system. You can also use chdir. ls The ls command shows you the files in your current directory. Used with certain options, it lets you see file sizes, when files where created and file permissions. For example, ls ~ shows you the files that are in your home directory. cp The cp command is used to make copies of files and…

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 or the like. We’ve created each of the two encounters as a defined set of functions, along with a list of possible choices under the cmdlist list, and cmd variable, of which is also a defined function. Expanding on this is quite easy, just map out each encounter and choice…

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 change the screen resolution if needed; we’re currently running it at 800 x 600.…

We’re going to finish off by looking at some interesting coding elements that you can incorporate into your own unique projects and code. In this section you’ll find code for creating a loading screen for your content, text animations using ASCII art, clever ways in which you can include animated sections at the command prompt, and even code that can track the International Space Station in realtime, while displaying both the astronauts on board and its current latitude and longitude. There are also pages of common, and language specific, mistakes to help you avoid, and create, error-free and effective code in the future.…

DEF BEGINNER(MISTAKES=10) Here are ten common Python programming mistakes most beginners find themselves making. Being able to identify these mistakes will save you headaches in the future. VERSIONS To add to the confusion that most beginners already face when coming into programming, Python has two live versions of its language available to download and use. There is Python version 2.7.x and Python 3.6.x. The 3.6.x version is the most recent, and the one we’d recommend starting. But, version 2.7.x code doesn’t always work with 3.6.x code and vice versa. THE INTERNET Every programmer has and does at some point go on the Internet and copy some code to insert into their own routines. There’s nothing wrong with using others’ code, but you need to know how the code works and…

“It’s up to you how far to take your coding adventure!” MORE THAN CODE For those of you old enough to remember the ‘80s, the golden era of home computing, the world of computing was a very different scene to how it is today. 8-bit computers that you could purchase as a whole, as opposed to being in kit form and you having to solder the parts together, were the stuff of dreams; and getting your hands on one was sheer bliss contained within a large plastic box. However, it wasn’t so much the new technology that computers then offered, moreover it was the fact that for the first time ever, you could control what was being viewed on the ‘television’. Instead of simply playing one of the thousands of…

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 software to consider. Then you access the Internet and discover that there are countless coding tutorials available, for the language in which you’ve decided you want to program, alongside even more examples of code. It’s all a little too much at times. The trick is to slow down and, to begin with, not look too deeply into coding. Like all good projects, you need a solid foundation on which to build your skill and to have all the necessary…

PYTHON POWER Ever since the earliest home computers were available, enthusiasts, users and professionals have toiled away until the wee hours, slaving over an overheating heap of circuitry to create something akin to magic. These pioneers of programming carved their way into a new frontier, forging small routines that enabled the letter ‘A’ to scroll across the screen. It may not sound terribly exciting to a generation that’s used to ultra high-definition graphics and open world, multiplayer online gaming. However, forty-something years ago it was blindingly brilliant. Naturally these bedroom coders helped form the foundations for every piece of digital technology we use today. Some went on to become chief developers for top software companies, whereas others pushed the available hardware to its limits and founded the billion pound gaming…

INSTALLING PYTHON 3.X Microsoft Windows doesn’t come with Python preinstalled as standard, so you’re going to have 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 3.7.3, or more, as long as it’s Python 3, the code in this book will work fine. STEP 2 Click the download button for version 3.x, and save the file to your Downloads folder. When the file is downloaded, double-click the executable and the Python installation wizard will launch. From here you have two choices: Install Now and Customise…

IT’S ALL MATHS, MAN You can get some really impressive results from the mathematical powers of Python, as maths is the driving force behind the code with most, if not all, programming languages. 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, we’re going to use the Shell. If you’ve opted to use a third-party text editor, note that you need to get to the IDLE Shell for this part of the tutorial. STEP 2 In the Shell enter the following: As you can see, Python can handle some quite large numbers. STEP 3 You can use all the customary Mathematical operations: divide, multiply, brackets and so on. Practise with a few, for example:…

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 default; the Math module is a prime example. Sadly, other modules aren’t always available. A good example on non-Pi platforms is the Pygame module, which contains many functions to help create games. Try: import pygame. STEP 3 The result is an error in the IDLE…

Data is everything. It’s more valuable than gold or oil. With data, governments can change the world, politicians can rise or fall, and companies, large or small, can impact our future in ways we wouldn’t have imagined just a few years ago. Data is power, and learning how to manipulate and control it are essential aspects of any coding language. Here we’ll take a look at how you can use date and time functions, write to files in your system, and even create graphical user interfaces that will take your coding skills to new levels and open more doors for you.…

EXCEPTIONAL OBJECTS Rather than stop the flow of your code, Python includes exception objects, which handle unexpected errors in the code. We 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 comes across something that’s inherently wrong with the code. However, we can create our own exceptions that are designed to contain the potential error and react to it, as opposed to letting the code fail. STEP 3 We can use the functions raise exception…

LIGHTS, CAMERA, ACTION The Tkinter module is an ideal starting point to 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 both a canvas (window) and the ball to animate: STEP 2 Save and Run the code. A blank window will appear, with a red ball sitting in the upper left corner of the window. While great, it’s not very animated. Let’s add the following code: STEP 3 Insert the new code between the ball1 = canvas.create_oval(5,5,60,60, fill=’red’) line, and the gui.mainloop() line. Save it and Run. You will now see the ball move from the top left corner…

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 that modifies the behaviour of the command. STEP 2 The “-l” argument lists files and directories in long format. Each file and directory is now on a single line, and before each file is a lot of text. First you’ll see lots of…

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 Files and directories are moved using the mv command. This is different to the commands we’ve looked at so far because it has two arguments (remember Linux command line is command, option, argument). The first argument is the source (the file or directory to be…

WHAT IS A USER? An important part of using Linux is the concept of users and understanding which user you are and which group you belong to. Like all modern computers, you can have multiple user accounts with each having different levels of access. STEP 1 The first thing you need to do is get a concept of which user you are. Enter: whoami into the command line and press return. It should say “pi” (unless you set up your account name differently during setup). The “whoami” command might seem a bit simplistic, but it comes in very handy sometimes. STEP 2 When you are working in Linux, from time to time a ‘Permission denied’ error will occur, typically when you try to create, edit or execute (run) a file…

MORE FUN, YAY Since the Terminal session is already open, and your keyboard digits are nicely warmed up, here are another two pages of Terminal nonsense. STEP 1 Remember the old ZX Spectrum days of computing, when you could type in 10 print “Hello”, 20 goto 10 and Hello would list down the screen? Well, in Raspbian you can do the same. Simply enter: yes followed by some text, i.e. yes Raspberry Pi is ace. It keeps going until you press Ctrl+C. STEP 2 The Matrix was one of the most visually copied films ever released and there’s even a version of the Matrix code available for Linux. Install it with: sudo apt-get install cmatrix. When it’s done enter: cmatrix and follow the white rabbit, Neo. Unlike the real Matrix…

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 one or more files to another location crontab Schedule a command to run at a later time csplit Split a file into context-determined pieces cut Divide a file into several parts D date Display or change the date & time dc Desk calculator dd Data Dump, convert and copy a file diff Display the differences between two files dirname Convert…

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 of the code creates the variables for the number of guesses used, along with the name of the player, and also sets up the random number between 1 and 30. If you want a wider range of random number selection, then increase the number=random.randint(1, 30) end value of…

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 incredibly 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 can output the chosen password to a file, then securely compress it using the previous random number generator as a file password and send it to a user for their new password. An interesting aspect to this code is the ability to introduce a loop and print any number of random…

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 come from the large set of variables called in the second section of the code and the duration is through the t variable set at the start of the code. There’s a half-second, using the…

LOAD”” Back in the 80s, in the 8-bit home computing era, loading screens were often used to display the cover of a game as it loaded from tape. The image would load itself in, usually one-line-at-a-time, then proceed to colour itself in while the loading raster bars danced around in the borders of the screen. Loading screens were a part of the package, and the buy-in for the whole game as an experience. Some loading screens featured animations, or a countdown for time remaining as the game loads, while others even went so far as to include some kind of playable game. The point being: a loading screen is not just an artistic part of computing history, but an introduction to the program that’s about to be run. While these…

ASCII ANIMATION Let’s assume you wanted to create an animated ASCII Happy Birthday Python script, with the words Happy and Birthday alternating in appearance. Here’s how it’s done. STEP 1 First we need to create some ASCII-like text, head over to http://patorjk.com/software/taag. This is an online Text to ASCII generator, created by Patrick Gillespie. Start by entering Happy into the text box, the result will be displayed in the main window. You can change the font with the drop-down menu, to the side of the text box; we’ve opted for Big. STEP 2 Now create a folder in your Python code directory on your computer (call it Test, for now), and open either Notepad for a Windows 10 computer, or, if you’re using Linux, then the currently installed text editor.…