Indholdsfortegnelse for Issue 6 i Python & C++ The Complete Manual

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…

INSTALLING PYTHON Apple’s operating system comes with Python installed, so you don’t need to install it separately. However, Apple doesn’t update Python very often and you’re probably running an older version. So it makes sense to check and update first. STEP 1 Open a new Terminal window by clicking Go > Utilities, then double-click the Terminal icon. Now enter: python --version. You should see “Python 2.5.1” and even later, if Apple has updated the OS and Python installation. Either way, it’s best to check for the latest version. STEP 2 Open Safari and head over to www.python.org/downloads. Just as with the Windows setup procedure on the previous pages, you can see two yellow download buttons: one for Python 3.6.2, and the other for Python 2.7.13. Note, that version numbers may…

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…

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…

C++ is a high level programming language that’s used in a multitude of technologies. Everything from your favourite mobile app, console and PC game to entire operating systems, all are developed using C++ and a collection of software development kits and custom libraries. C++ is the driving force behind most of what you use on a daily basis, which makes it a complex and extraordinarily powerful language to get to grips with. In this section, we look at how to install a C++ IDE and compiler on your computer.…

CODE::BLOCKS Code::Blocks is a free C++, C and Fortran IDE that’s feature rich and easily extendible with plug-ins. It’s easy to use, comes with a compiler and has a vibrant community behind it. STEP 1 Start by visiting the Code::Blocks download site, at www.codeblocks.org/downloads. From there, click on the ‘Download the binary releases’ link to be taken to the latest downloadable version for Windows. STEP 2 You can see that there are several Windows versions available. The one you want to download has ‘mingw-setup.exe’ at the end of the current version number. At the time of writing this is: codeblocks-17.12mingw-setup.exe. The difference is that the mingw-setup version includes a C++ compiler and debugger from TDM-GCC (a compiler suite). STEP 3 When you’ve located the file, click on the Sourceforge.net link…

DEVELOPING C++ Here are ten great C++ IDEs that are worth looking into. You can install one or all of them if you like, but find the one that works best for you. ECLIPSE Eclipse is a hugely popular C++ IDE that offers the programmer a wealth of features. It has a great, clean interface, is easy to use and available for Windows, Linux and Mac. Head over to www.eclipse.org/downloads/ to download the latest version. If you’re stuck, click the Need Help link for more information. GNAT The GNAT Programming Studio (GPS) is a powerful and intuitive IDE that supports testing, debugging and code analysis. The Community Edition is free, whereas the Pro version costs; however, the Community Edition is available for Windows, Mac, Linux and even the Raspberry Pi.…

GREETINGS FROM C++ Compiling and executing C++ code from Code::Blocks is extraordinarily easy; just a matter of clicking an icon and seeing the result. Here’s how it’s done. STEP 1 Open Code::Blocks, if you haven’t already, and load up the previously saved Hello World code you created. Ensure that there are no visible errors, such as missing semicolons at the end of the std::cout line. STEP 2 If your code is looking similar to the one in our screenshot, then look to the menu bar along the top of the screen. Under the Fortran entry in the topmost menu you can see a group of icons: a yellow cog, green play button and a cog/play button together. These are Build, Run, Build and Run functions. STEP 3 Start by clicking…

THE VALUE OF DATA There are many different data types available for the programmer in C++, such as an integer, floating point, Boolean, character and so on. It’s widely accepted that there are seven basic data types, often called Primitive Built-in Types; however, you can create your own data types should the need ever arise within your code. The seven basic data types are: These basic types can also be extended using the following modifiers: Long, Short, Signed and Unsigned. Basically this means the modifiers can expand the minimum and maximum range values for each data type. For example, the int data type has a default value range of -2147483648 to 2147483647, a fair value, you would agree. Now, if you were to use one of the modifiers, the range…

HELLO, DAVE You have already used cout, the standard output stream, throughout our code. Now you’re going to be using cin, the standard input stream, to prompt a user response. STEP 1 Anything that you want the user to input into the program needs to be stored somewhere in the system memory, so it can be retrieved and used. Therefore, any input must first be declared as a variable, so it’s ready to be used by the user. Start by creating a blank C++ file with headers. STEP 2 The data type of the variable must also match the type of input you want from the user. For example, to ask a user their age, you would use an integer like this: STEP 3 The cin command works in the…

FSTREAMS There are two main data types within the fstream library that are used to open a file, read from it and write to it, ofstream and ifstream. Here’s how they work. STEP 1 The first task is to create a new C++ file and along with the usual headers you need to include the new fstream header: STEP 2 Begin by asking a user for their name and writing that information to a file. You need the usual string to store the name, and getline to accept the input from the user. STEP 3 We’ve included comments in the screenshot of step 2 to help you understand the process. You created a string called name, to store the user’s inputted name. You also created a text file called name.txt…

DO LOOPS The good thing about a do… while loop is that it’s guaranteed to run through at least once. It’s structure is: do, followed by statements, while condition is true. This is how it works. STEP 1 Begin with a new, blank C++ file and enter the standard headers: STEP 2 Begin with a simple number count: STEP 3 Now, here’s a look at the structure of a do… while loop. First you create an integer called num, with the value of 1. Now the do… while loops begins. The code inside the body of the loop is executed at least once, then the condition is checked for either true or false. STEP 4 If the condition is true, the loop is executed. This continues until the condition is…

VOID(C++, MISTAKES) Admittedly it’s not just C++ beginners that make the kinds of errors we outline on these pages, even hardened coders are prone to the odd mishap here and there. Here are some common issues to try and avoid. UNDECLARED IDENTIFIERS A common C++ mistake, and to be honest a common mistake with most programming languages, is when you try and output a variable that doesn’t exist. Displaying the value of x on-screen is fine but not if you haven’t told the compiler what the value of x is to begin with. SEMICOLONS Remember that each line of a C++ program must end with a semicolon. If it doesn’t then the compiler treats the line with the missing semicolon as the same line with the next semicolon on. This…

There are many different programming languages available to learn and use. Some are complex and incredibly powerful and some are extremely basic and used as minor utilities for operating systems. Python sits somewhere in the middle, combining ease of use with a generous helping of power that allows the user to create minor utilities, a range of excellent games and performanceheavy computational tasks. However, there’s more to Python than simply being another programming language. It has a vibrant and lively community behind it that shares knowledge, code and project ideas; as well as bug fixes for future releases. It’s thanks to this community that the language has grown and thrived and now it’s your turn to take the plunge and learn how to program in Python. The first half of…

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. 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 in a bowl. Add 100 grams of butter to the bowl. Add 100 millilitres of milk. Bake for half an hour. CODE Just like a recipe, a program consists of instructions that you follow in order. A program that describes a cake might run like this: PROGRAM COMMANDS You might not understand some of the Python commands, like bowl.append and cake.cook(bowl). The first is a list, 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 we will stick to Linux Mint 18.1 for this particular tutorial. STEP 1 First you need to ascertain which version of Python is currently installed in your Linux system; as we mentioned, we’re going to be using Linux Mint 18.1 for this section. As with macOS, drop into a Terminal by pressing Ctrl+Atl+T. 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. Ours in this particular case is Python 2.7.12. STEP 3 Some Linux distros will automatically update the installation of Python to…

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…

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…

Data is everything. With it you can display, control, add, remove, create and manipulate Python to your every demand. Over these coming pages we look at how you can create lists, tuples, dictionaries and multi-dimensional lists; and see how to use them to forge exciting and useful programs. Then, you can learn how to use date and time functions, write to files in your system and even create graphical user interfaces that take your coding skills to new levels and into new project ideas.…

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…

C EVERYTHING Due to how complex the language can be, and its power and performance, C++ is often used to develop games, programs, device drivers and even entire operating systems. Dating back to 1979, the start of the golden era of home computing, C++, or rather C with Classes, was the brainchild of Danish computer scientist Bjarne Stroustrup while working on his PhD thesis. Stroustrup’s plan was to further the original C language, which was widely used since the early seventies. C++ proved to be popular among the developers of the ‘80s, since it was a much easier environment to get to grips with and more importantly, it was 99% compatible with the original C language. This meant that it could be used beyond the mainstream computing labs and by…

XCODE Apple’s Xcode is primarily designed for users to develop apps for macOS, iOS, tvOS and watchOS applications in Swift or Objective-C but you can use it for C++ too. STEP 1 Start by opening the App Store on your Mac, Apple Menu > App Store. In the Search box enter ‘Xcode’ and press Return. There are many suggestions filling the App Store window but it’s the first option, Xcode, that you need to click on. STEP 2 Take a moment to browse through the app’s information, including the compatibility, to ensure you have the correct version of macOS. Xcode requires macOS 10.12.6 or later to install and work. STEP 3 When you’re ready, click on the Get button which then turns into Install App. Enter your Apple ID and…

HELLO, WORLD! It’s traditional in programming for the first code to be entered to output the words ‘Hello, World!’ to the screen. Interestingly, this dates back to 1968 using a language called BCPL. STEP 1 As mentioned, we’re using Windows 10 and the latest version of Code::Blocks for the rest of the C++ code in this book. Begin by launching Code::Blocks. When open, click on File > New > Empty File or press Ctrl+Shift+N on the keyboard. STEP 2 Now you can see a blank screen, with the tab labelled *Untitled1, and the number one in the top left of the main Code::Blocks window. Begin by clicking in the main window, so the cursor is next to the number one, and entering: STEP 3 At the moment it doesn’t look…

STRING THEORY There are different ways in which you can create a string of characters, which historically are all carried over from the original C language, and are still supported by C++. STEP 1 To create a string you use the char function. Open a new C++ file and begin with the usual header: STEP 2 It’s easy to confuse a string with an array. Here’s an array, which can be terminated with a null character: STEP 3 Build and run the code, and ‘Welcome’ appears on the screen. While this is perfectly fine, it’s not a string. A string is a class, which defines objects that can be represented as a stream of characters and doesn’t need to be terminated like an array. The code can therefore be represented…

ESCAPE SEQUENCE When used in something like a cout statement, character literals are also called Escape Sequence Codes. They allow you to insert a quote, an alert, new line and much more. STEP 1 Create a new C++ file and enter the relevant headers: STEP 2 You’ve already experienced the \n character literal placing a new line wherever it’s called. The line: cout << “Hello\n” << “I’m a C++\n” << “Program\n”; outputs three lines of text, each starting after the last \n. STEP 3 If you wanted to insert speech quotes inside a cout statement, you would have to use a backslash as it already uses quotes: STEP 4 There’s even a character literal that can trigger an alarm. In Windows 10, it’s the notification sound that chimes when you…

A while loop’s function is to repeat a statement, or a group of statements, while a certain condition remains true. When the while loop starts, it initialises itself by testing the condition of the loop and the statements within, before executing the rest of the loop. TRUE OR FALSE? While loops are one of the most popular form of C++ code looping. They repeatedly run the code contained within the loop while the condition is true. Once it proves false, the code continues as normal. STEP 1 Clear what you’ve done so far and create a new C++ file. There’s no need for any extra headers at the moment, so add the standard headers as per usual: STEP 2 Create a simple while loop. Enter the code below, build and…

IF ONLY If uses a Boolean expression within its statement. If the Boolean expression is true, the code within the statement is executed. If not, then the code after the statement is executed instead. STEP 1 First, create a new C++ file and enter the relevant standard headers, as usual: STEP 2 If is best explained when you use a number-based condition: STEP 3 What’s going on here? To begin, an integer called num was created and assigned with the value of 1. The if statement comes next, and in this case we’ve instructed the code that if the condition, the value, of num is less than 1, then the code within the braces should be executed. STEP 4 The second cout statement displays the current value of num and…

#INCLUDE<KEEP ON LEARNING> What can you do to further your skills, learn new coding practises, experiment and present your code and even begin to help others using what you’ve experienced so far? TWITTER Twitter isn’t all trolls and antagonists, among the well-publicised vitriol are some genuine people who are more than willing to spread their coding knowledge. We recommend you find a few who you can relate to and follow them. Often they post great tips, hacks and fixes for common coding problems. KEEP CODING If you’ve mastered Python fairly well, then turn your attention to C++ or even C#. Still keep your Python skills going but learning a new coding language keeps the old brain ticking over nicely and give you a view into another community, and how they…

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, multi-player 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.x (in our case this is Python 3.6.2 but as mentioned you may see later versions of 3). 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 Installation. We recommend opting for the Customise Installation link. STEP 3 Choosing the Customise option allows you to specify certain parameters,…

STARTING PYTHON We’re not going to go into the details of getting the Raspberry Pi up and running, there’s plenty of material already available on that subject. However, once you’re ready, fire up your Pi and get ready for coding. 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…

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:…

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…

C++ SETUPS Most, if not all, operating systems have C++ in their code, so it stands to reason that you can learn to program in C++ no matter what OS you’re currently using. □ COMPUTER Unless you fancy writing out your C++ code by hand on a sheet of paper (which is something many older coders used to do), a computer is an absolute must have component. PC users can have any recent Linux distro or Windows OS, Mac users the latest macOS. □ AN IDE Just as with Python, an IDE is used to enter and execute your C++ code. Many IDEs come with extensions and plugins that help make it work better, or add an extra level of functionality. Often, an IDE provides enhancements depending on the core…

LINUX++ If you’re not familiar with Linux, then we recommend taking a look at one of our Linux titles from the BDM Publications range. If you have a Raspberry Pi, the commands used below work just fine and for this example we’re using Linux Mint. STEP 1 The first step is to ensure Linux is ready for your C++ code, so check the system and software are up to date. Open a Terminal and enter: sudo apt-get update && sudo apt-get upgrade. Then press Return and enter your password. These commands update the entire system and any installed software. STEP 2 Most Linux distros come preinstalled with all the necessary components to start coding in C++; however, it’s always worth checking to see if everything is present. Still within the…

THE DECLARATION OF VARIABLES You can declare a C++ variable by using statements within the code. There are several distinct types of variables you can declare. Here’s how it works. STEP 1 Open up a new, blank C++ file and enter the usual code headers: STEP 2 Start simple by creating two variables, a and b, with one having a value of 10 and the other 5. You can use the data type int to declare these variables. Within the curly brackets, enter: STEP 3 You can build and run the code but it won’t do much, other than store the values 10 and 5 to the integers a and b. To output the contents of the variables, add: STEP 4 Naturally you can declare a new variable, call it…

C++ = MC2 The basic mathematical symbols apply in C++ as they do in most other programming languages. However, by using the C++ Math Library, you can also calculate square roots, powers, trig and more. STEP 1 C++’s mathematical operations follow the same patterns as those taught in school, in that multiplication and division take precedence over addition and subtraction. You can alter that though. For now, create a new file and enter: STEP 2 While simple, it does get the old maths muscle warmed up. Note that we used a float for the numbers variable. While you can happily use an integer, if you suddenly started to use decimals, you would need to change to a float or a double, depending on the accuracy needed. Run the code and…

#DEFINE The pre-processors are instructions to the compiler to pre-process the information before it goes ahead and compiles the code. #include is a pre-processor as is #define. STEP 1 You can use the #define pre-processor to define any constants you want in our code. Start by creating a new C++ file complete with the usual headers: STEP 2 Now let’s assume your code has three different constants: length, width and height. You can define them with: STEP 3 Note the capitals for defined constants, it’s considered good programming practise to define all constants in capitals. Here, the assigned values are 50, 40 and 60, so let’s call them up: STEP 4 Build and run the code. Just as expected, it displays the values for each of the constants created. It’s…

LOOPY LOOPS The initialise stage of a for loop is executed only once and this sets the point reference for the loop. The condition is evaluated by the loop to see if it’s true or false and then the increment is executed. The loop then repeats the second and third stage. STEP 1 Create a new C++ file, with the standard headers: STEP 2 Start simple and create a for loop that counts from 1 to 30, displaying the value to the screen with each increment: STEP 3 Working through the process of the for loop, begin by creating an integer called num and assigning it a value of 1. Next, set the condition, in this case num being less than 30. The last stage is where you create the…

IF YES, ELSE NO There are two sections of code that can be executed depending on the outcome in an if… else statement. It’s quite easy to visualise once you get used to its structure. STEP 1 Begin with a new C++ file and the standard headers: STEP 2 Let’s expand the code from the If Statement on the previous page: STEP 3 The first line in the code creates the integer called num and gives it a value of 1. The if statement checks to see if the value of num is less than thirty and if it is it outputs “The number is less than 30!” to the console. STEP 4 The else companion to if checks if the number is greater than 30 and if so, then…

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…