Tabla de contenidos para issue 2 en Python Coding & Programming The Complete Manual

Unlock your imagination with Python… There are few coding languages that have enjoyed the success of Python. Thanks to Python’s unique development, everyone can learn the code that is: helping to drive such technological projects as the Large Hadron Collider, collating the petabytes of data that made up the first image of a Black Hole and creating the next generation of Artificial Intelligence. It doesn’t take long to get to grips with Python, but you need to start small. This guide will help you form the foundation of your Python coding future, from installing the language on to your computer, through to forming user interaction and complex variables. There’s so much you can do with Python and within these pages you’ll find everything you need to know to become a…

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 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…

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…

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…

WHAT IS PROGRAMMING? It helps to understand what a programming language is before you try to learn one, and Python is no different. Let’s take a look at how Python came about and how it relates to other languages. PYTHON A programming language is a list of instructions that a computer follows. These instructions can be as simple as displaying your name or playing a music file, or as complex as building a whole virtual world. Python is a programming language conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands as a successor to the ABC language. PROGRAMMING RECIPES Programs are like recipes for computers. A recipe to bake a cake could go like this: Put 100 grams of self-raising flour…

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 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, where you’re able to try out some simple code and processes. STEP 3 For example, in the Shell enter: 2+2 After pressing Enter,…

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 2 Just as before, we’re using a Raspberry Pi: Windows users will need to click the Start button and search for CMD, then click the Command Line returned search; and macOS users can get access to their command line by clicking Go > Utilities >…

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 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:…

TRUE CONDITIONS Keeping conditions simple to begin with makes learning to program a more enjoyable experience. Let’s start then by checking if something is TRUE, then doing something else if it isn’t. STEP 1 Let’s create a new Python program that will ask the user to input a word, then check it to see if it’s a four-letter word or not. Start with File > New File, and begin with the input variable: STEP 2 Now we can create a new variable, then use the len function and pass the word variable through it to get the total number of letters the user has just entered: STEP 3 Now you can use an if statement to check if the word_length variable is equal to four and print a friendly conformation…

PLAYING WITH PI For this example we’re going to create a program that will calculate the value of Pi to a set number of decimal places, as described by the user. It combines much of what we’ve learnt, and a little more. STEP 1 Start by opening Python and creating a New File in the Editor. First we need to get hold of an equation that can accurately calculate Pi without rendering the computer’s CPU useless for several minutes. The recommended calculation used in such circumstances is the Chudnovsky Algorithm, you can find more information about it at en.wikipedia.org/wiki/Chudnovsky_algorithm. STEP 2 You can utilise the Chudnovsky Algorithm to create your own Python script based on the calculation. Begin by importing some important modules and functions within the modules: This uses…

WORKING WITH LISTS Lists are extremely handy in Python. A list can be strings, integers and also variables. You can even include functions in lists, and lists within lists. STEP 1 A list is a sequence of data values called items. You create the name of your list followed by an equals sign, then square brackets and the items separated by commas; note that strings use quotes: STEP 2 Once you’ve defined your list you can call each by referencing its name, followed by a number. Lists start the first item entry as 0, followed by 1, 2, 3 and so on. For example: To call up the entire contents of the list. To call the third from zero item in the list (21 in this case). STEP 3 You…

STRING THEORIES You’ve already looked at some list functions, using .insert, .remove, and .pop but there are also functions that can be applied to strings. STEP 1 The main tool in the string function arsenal is .split(). With it you’re able to split apart a string of data, based on the argument within the brackets. For example, here’s a string with three items, each separated by a space: STEP 2 Now let’s turn the string into a list and split the content accordingly: Then enter the name of the new list, names, to see the three items. STEP 3 Note that the text.split part has the brackets, quotes, then a space followed by closing quotes and brackets. The space is the separator, indicating that each list item entry is separated…

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. 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: STEP 3 If…

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: 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. A new window will now open up and the ‘Turtle’ will draw a circle. STEP 3 The…

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.…

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 into the Shell, or as part of your code in the Editor. STEP 2 Importing the Math module 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 displays the sine of 2. STEP 3 As you will no doubt be aware…

PYGAMING Pygame isn’t an inherent module to Python but those using the Raspberry Pi will already have it installed. Everyone else will need to use: pip install pygame from the command prompt. STEP 1 Naturally you need to load up the Pygame modules into memory before you’re able to utilise them. Once that’s done Pygame requires the user to initialise it prior to any of the functions being used: STEP 2 Let’s create a simple game ready window, and give it a title: You can see that after the first line is entered, you need to click back into the IDLE Shell to continue entering code; also, you can change the title of the window to anything you like. STEP 3 Sadly you can’t close the newly created Pygame window…

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 is said to lead to wisdom, ML reportedly leads to knowledge and, thanks to Python, that gap is getting closer every day. APPLICATIONS Both AI and ML are hugely present in today’s technology. Where, just a few years ago, most of us associated AI with…

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…

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…

ALARMCLOCK.PY This code is designed for use in the command prompt, be that Windows, Linux or macOS. There are some instructions on how to use it in the main print section but essentially it’s: python3 AlarmClock.py 10 (to go off in ten minutes). Wakey Wakey There’s some good use of try and except blocks here, alongside some other useful loops that can help you get a firmer understanding of how they work in Python. The code itself can be used in a variety of ways: in a game where something happens after a set amount of time or simply as a handy desktop alarm clock for your tea break. Linux users, try making the alarm clock code into an alias, so you can run a simple command to execute it.…

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…

CALCULATOR.PY We created some function definitions to begin with, then lead on to the user menu and inputs. It’s an easy piece of code to follow and as such can also be expanded well too. Improved Calculations The obvious contender for improvement here is using the Create Your Own Modules route and extracting the function definitions as a module. You can then call the module and focus on the body of the code. The other area of improvement is code itself. Where there’s just a single shot at making a calculation, you could encase it in a while loop, so once a value is presented the user is sent back to the main menu. Perhaps, improvement to the Invalid Input section is worth looking into as well.…

Linux is a surprisingly powerful, fast, secure and capable operating system. It’s used as the OS of choice for the Raspberry Pi, in the form of Raspbian OS, as well as in some of the most unlikely places. Despite only enjoying a 1.96% share (according to netmarketshare.com) of the total desktop operating system market, Linux has a dedicated following of enthusiasts, users and contributors. It was created in 1991 by University of Helsinki student, Linus Torvalds, who had become frustrated with the limitations and licensing of the popular educational system Minix, a miniature version of the Unix operating system, in use at the time. Unix itself was released in the early ‘70s, as a multi-tasking, modular-designed operating system originally developed for programmers who needed a stable platform to code on.…

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…

TAKING COMMAND There are countless Linux tips, secrets, hacks and tricks out there. Some are very old, originating from Linux’s Unix heritage, while others are recent additions to Linux lore. Here are our ten favourite tips and tricks. EASTER EGGS Emacs text editor, is a great piece of software but did you know it also contains a hidden Easter Egg? With Emacs installed (sudo apt-get install emacs24), drop to a Terminal session and enter: Dunnet is a text adventure written by Ron Schnell in 1982, and hidden in Emacs since 1994. MOON BUGGY Based on the classic 1982 arcade game, Moon Patrol, Moon Buggy appeared on home computers in 1985 amid much praise. It’s a cracking Atari game available in the Linux Terminal by entering: Then: Enjoy. TERMINAL BROWSING Ever…

Python is a high-level, general-purpose programming language that was developed by Guido van Rossum in the late eighties and is based upon a number of other languages, while being the successor to the popular ABC language. It has been devised to work on a human level, so it’s readable and understandable without needing to delve into obscure volumes of machine code, hexadecimal characters, or even ones and zeros. It’s clear, logical, comprehensive, powerful and functional, yet also easy to follow and learn. You will find Python at the heart of some of the most interesting and cutting-edge technologies in the world. It’s the code that binds supercomputer algorithms together; it’s used in the space industry, and in science and engineering. AI, and the likes of Alexa and Siri, Cortana and…

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 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…

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…

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.…

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, 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…

PLAYING WITH PYTHON With most languages, computer or human, it’s all about remembering and applying the right words to the right situation. You’re not born knowing these words, so you need to learn them. STEP 1 If you’ve closed Python 3 IDLE, reopen it in whichever operating system version you prefer. In the Shell, enter the familiar following: STEP 2 Just as predicted, the word Hello appears in the Shell as blue text, indicating output from a string. It’s fairly straightforward and doesn’t require too much explanation. Now try: STEP 3 You can see that instead of the number 4, the output is the 2+2 you asked to be printed to the screen. The quotation marks are defining what’s being outputted to the IDLE Shell; to print the total of…

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 brain (or not). STEP 2 In the Shell enter the following: You can see that Python can handle some quite large numbers. STEP 3 You can use all the usual mathematical operations: divide, multiply, brackets and so on. Practise with a few, for example: STEP 4 You’ve…

USER FRIENDLY The type of input you want from the user will depend greatly on the type of program you’re coding. For example, a game may ask for a character’s name, whereas a database can ask for personal details. STEP 1 If it’s not already, open the Python 3 IDLE Shell, and start a New File in the Editor. Let’s begin with something really simple, enter: STEP 2 Save and execute the code, and as you already no doubt suspected, in the IDLE Shell the program will ask for your first name, storing it as the variable firstname, followed by your surname; also stored in its own variable (surname). STEP 3 Now that we have the user’s name stored in a couple of variables we can call them up whenever…

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 being 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…

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 which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways, a black hole acts like…

THE IMMUTABLE TUPLE Reasons for having tuples vary depending on what the program is intended to do. Normally, a tuple is reserved for something special but they’re also used for example, in an adventure game, where non-playing character names are stored. STEP 1 A tuple is created the same way as a list but in this instance you use curved brackets instead of square brackets. For example: STEP 2 Just as with lists, the items within a named tuple can be indexed according to their position in the data range, i.e.: However, any attempt at deleting or adding to the tuple will result in an error in the Shell. STEP 3 You can create grouped tuples into lists that contain multiple sets of data. For instance, here is a tuple…

STRING FORMATTING Since Python 3, string formatting has become a much neater process, using the .format function combined with curly brackets. It’s a more logical and better formed approach than previous versions. STEP 1 The basic formatting in Python is to call each variable into the string using the curly brackets: STEP 2 Remember to close the print function with two sets of brackets, as you’ve encased the variable in one, and the print function in another. You can include multiple cases of string formatting in a single print function: STEP 3 You can of course also include integers into the mix: STEP 4 There are many different ways to apply string formatting, some are quite simple, as we’ve shown you here; others can be significantly more complex. It all…

WRITE AND CLOSE The write() function is slightly more complex than read(). Along with the filename you must also include an access mode which determines whether the file in question is in read or write mode. STEP 1 Start by opening IDLE and enter the following: Change the destination from/home/pi/Documents to your own system. This code will create a text file called text.txt in write mode using the variable ‘t’. If there’s no file of that name in the location, it will create one. If one already exits, it will overwrite it, so be careful. STEP 2 You can now write to the text file using the write() function. This works opposite to read(), writing lines instead of reading them. Try this: Note the 109. It’s the number of characters…

LOGGING IN For this example, let’s look to a piece of code that creates user logins and then allows them to log into the system and write the time they logged in at. You can even include an option to quit the program by pressing ‘q’. STEP 1 Begin by importing the Time module, creating a new dictionary to handle the usernames and passwords and creating a variable to evaluate the current status of the program: STEP 2 Next you need to define some functions. You can begin by creating the main menu, where all users will return to after selecting the available options: STEP 3 The global status statement separates a local variable from one that can be called throughout the code, this way you can use the q=quit…

WORKING WITH DATES The Calendar module is built into Python 3. However, if for some reason it’s not installed you can add it using pip install calendar as a Windows administrator, or sudo pip install calendar for Linux and macOS. STEP 1 Launch Python 3 and enter: import calendar to call up the module and its inherent functions. Once it’s loaded into memory, start by entering: STEP 2 You can see that the days of September 2019 are displayed in a wall calendar fashion. Naturally you can change the 2019, 9 part of the second line to any year and month you want, a birthday for example (1973, 6). The first line configures TextCalendar to start its weeks on a Sunday; you can opt for Monday if you prefer. STEP…

RANDOM NUMBERS There are numerous functions within the Random module, which when applied can create some interesting and very useful Python programs. STEP 1 Just as with other modules you need to import random before you can use any of the functions we’re going to look at in this tutorial. Let’s begin by simply printing a random number from 1 to 5: STEP 2 In our example the number four was returned. However, enter the print function a few more times and it will display different integer values from the set of numbers given, zero to five. The overall effect, although pseudorandom, is adequate for the average programmer to utilise in their code. STEP 3 For a bigger set of numbers, including floating point values, you can extend the range…

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 in the upper left corner of the window. While this is 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…

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 to your own…

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 through a Tkinter window or even the Ticker window that’s available on Page 128. Furthermore, the core of the code can be used in a text adventure game, where the character fights something and their health, along with the enemy’s, is reduced by a…

FILEBROWSER.PY Tkinter is the main module in use here but we’re also using idlelib, so you may need to pip install any extras if the dependencies fail when you execute the code. Advanced Filing When executed, the code will display the current directory’s contents. If you want to see the contents of another directory, you can run the code from a command line within the chosen directory; just remember to call the code from where it’s located on your system, as per the second screenshot. You can also double-click any of the file names shown in the directory tree and rename them. This is an interesting piece of code and one that you can insert into your own programs. You can extend the code to include a user specified directory…

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.…

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…

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…

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 right-facing 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…

HEY, MAN! The man pages are one of the best features of Linux, and as a built-in tool it’s invaluable for both beginner and senior level Linux administrators. Let’s see how it works. STEP 1 Linux has a built-in manual, known as man for short. Using the man command you can obtain information on all the Linux commands we’ve talked about. Simply enter: man and the name of the command you want to learn more about. Start by entering: man ls in the command line. STEP 2 The man pages are a bit more detailed than you might be used to. First you have a name, which tells you what the command is called; in this case “list directory contents” and then the synopsis shows you how it works. In…

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…

“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…

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. 16,000 There are over 16,000 Python jobs posted every six months in the UK. PYTHON SKILL-BASED POSITIONS ARE THE 16th MOST SOUGHT-AFTER JOBS IN THE UK. Python Data Science is thought to become the most sought-after job in the coming years. Google is the top company for hiring Python…

Sounds good, but what exactly is a Virtual Machine (VM) and how does it work? The official definition of a virtual machine is ‘an efficient, isolated duplicate of a real computer machine’. This basically means that a virtual machine is an emulated computer system that can operate in exactly the same way as a physical machine, but within the confines of a dedicated virtual machine operator, or Hypervisor. The Hypervisor itself, is an app that will allow you to install a separate operating system, creating a virtual computer system within itself, complete with access to the Internet, your home network and so on. The Hypervisor will take resources from the host system - your physical computer, to create the virtual computer. This means that part of your physical computer’s: memory,…

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 inspect your program code and the values within the code, as well as offering advanced features. There are many different IDEs available, so find the one that works for you and gives the…

PYTHON PENGUIN Linux is such a versatile operating system that it’s often difficult to nail down just one-way of doing something. Different distributions go about installing software in different ways, so for this particular tutorial we will stick to Linux Mint. STEP 1 First you need to ascertain which version of Python is currently installed in your Linux system. To begin with, drop into a Terminal session from your distro’s menu, or hit the Ctrl+Alt+T keys. STEP 2 Next, enter: python --version into the Terminal screen. You should have the output relating to version 2.x of Python in the display. Most Linux distro come with both Python 2 and 3 by default, as there’s plenty of code out there still available for Python 2. Now enter: python3 --version. STEP 3…

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 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; much in the same vein as Sublime. You enter code as you would within the Shell, so taking an example from…

#COMMENTS! Programmers use a method of keeping their code readable by commenting on certain sections. If a variable is used, the programmer comments on what it’s supposed to do, for example. It’s just good practise. STEP 1 Start by creating a new instance of the IDLE Editor (File > New File) and create a simple variable and print command: Save the file and execute the code. STEP 2 Running the code will return the line: The value of A is, 10 into the IDLE Shell window, which is what we expected. Now, add some of the types of comments you’d normally see within code: STEP 3 Resave the code and execute it. You can see that the output in the IDLE Shell is still the same as before, despite the…

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() 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 to…

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 to find in simple dozen-line code, imagine having to debug multi-thousand line code. STEP 2 The most common of errors is the typo, as we’ve mentioned. The typos are often at the command level: mistyping the print command for example. However, they also occur when you have…

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.…

KEY PAIRS A dictionary is like a list but instead each data item comes as a pair, these are known as Key and Value. The Key part must be unique and can either be a number or string whereas the Value can be any data item you like. STEP 1 Let’s say you want to create a phonebook in Python. You would create the dictionary name and enter the data in curly brackets, separating the key and value by a colon Key:Value. For example: STEP 2 Just as with most lists, tuples and so on, strings need be enclosed in quotes (single or double), whilst integers can be left open. Remember that the value can be either a string or an integer, you just need to enclose the relevant one…

TIME LORDS The Time module contains functions that help you retrieve the current system time, reads the date from strings, formats the time and date and much more. STEP 1 First you need to import the Time module. It’s one that’s built-in to Python 3 so you shouldn’t need to drop into a command prompt and pip install it. Once it’s imported, you can call the current time and date with a simple command: STEP 2 The time function is split into nine tuples, these are divided up into indexed items, as with any other tuple, and shown in the screen shot below. STEP 3 You can see the structure of how time is presented by entering: The output is displayed as such: ‘time.struct_time(tm_year=2017, tm_mon=9, tm_mday=7, tm_hour=9, tm_min=6, tm_sec=13, tm_wday=3,…

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 comes across something that’s inherently wrong with the code. However, you can create your own exceptions that are designed to contain the potential error and react to it, as opposed to letting the code fail. STEP 3 You can use the functions raise exception…

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 games these days are created using a range of development tools. These tools can be off-the-shelf engines, such as the Unreal Engine, while others are custom built around an original product, such as the world generating engine that Bethesda use for the…

INTO THE SYSTEM One of the primary features of the OS module is the ability to list, move, create, delete and otherwise interact with files stored on the system, making it the perfect module for backup code. STEP 1 You can start the OS module with some simple functions to see how it interacts with the operating system environment that Python is running on. If you’re using Linux or the Raspberry Pi, try this: STEP 2 The returned result from printing the variable home is the current user’s home folder on the system. In our example that’s/home/pi; it will be different depending on the user name you log in as and the operating system you use. For example, Windows 10 will output: C:\Program Files (x86)\ Python36-32. STEP 3 The Windows…

GETTING GUI Tkinter is easy to use but there’s a lot more you can do with it. Let’s start by seeing how it works and getting some code into it. Before long you will discover just how powerful this module really is. STEP 1 Tkinter is usually built into Python 3. However, if it’s available when you enter: import tkinter, then you need to pip install tkinter from the command prompt. We can start to import modules differently than before, to save on typing and by importing all their contents: STEP 2 It’s not recommended to import everything from a module using the asterisk but it won’t do any harm normally. Let’s begin by creating a basic GUI window, enter: This creates a small, basic window. There’s not much else…

BUILDING MODULES Modules are Python files, containing code, that you save using a .py extension. These are then imported into Python using the now familiar import command. STEP 1 Let’s start by creating a set of basic mathematics functions. Multiply a number by two, three and square or raise a number to an exponent (power). Create a New File in the IDLE and enter: STEP 2 Under the above code, enter functions to call the code: Save the program as basic_math.py and execute it to get the results. STEP 3 Now you’re going to take the function definitions out of the program and into a separate file. Highlight the function definitions and choose Edit > Cut. Choose File > New File and use Edit > Paste in the new window.…

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 the CLS command clears the screen, whereas in Linux and macOS, the Clear command wipes the screen. If the code tries to run CLS when being used in Linux or macOS, an error occurs, which then prompts it to run the Clear command instead. 4 These are the options, from 1 to 12. Each executes…

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 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…

MOUSETURTLE.PY The first piece of code presents the standard Turtle window. Press Space and then click anywhere on the screen for the Turtle to draw to the mouse pointer. The second allows you to click the Turtle and drag it around the screen; but be warned, it can crash Python. 1st Code Example: 2nd Code Example: Ninja TurtleMouse This code utilises some interesting skills. Obviously it will stretch your Python Turtle skills to come up with any improvements, which is great, but it could make for a nice piece of code to insert into something a young child will use. Therefore it can be a fantastic project for a younger person to get their teeth into; or perhaps even as part of a game where the main character is tasked…

DIGCLOCK.PY This is a surprisingly handy little script and one that we’ve used in the past instead of relying on a watch or even the clock in the system tray of the operating system. Tick Tock This is a piece of code we’ve used many times in the past to keep track of time while working on multiple monitors and with just a quick glance to where we’ve placed it on the screen. The Tkinter box can be moved around without affecting the time, maximised or closed by the user at will. We haven’t given the Tkinter clock window a title, so you can add to that easily enough by snipping the code from other examples in this book. Another area of improvement is to include this code when Windows…

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 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…

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.…

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…

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:…

Argument The detailed extra information used by Python to perform more detailed commands. Can also be used in the command prompt to specify a certain runtime event. Block Used to describe a section or sections of code that are grouped together. Break A command that can be used to exit a for or while loop. For example, if a key is pressed to quit the program, Break will exit the loop. Class A class provides a means of bundling data and functionality together. They are used to encapsulate variables and functions into a single entity. Comments A comment is a section of real world wording inserted by the programmer to help document what’s going on in the code. They can be single line or multi-line and are defined by a…