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

BDM’s Complete Manual Series Python & C++ Unleash the power of Python and C++ Having a basic knowledge of programming can open many different doors for the newcomer to explore. You can gain a better understanding of how hardware and software work together, how your computer or device functions and how incredible open-world gaming environments are converted from ones and zeros to what’s on your monitor or TV. Technology is everywhere and it’s all connected through programming. Your TV, microwave, in-car entertainment and the Internet itself are all reliant on good programming to make them work the way you want them to. Within these pages are the building blocks to help you take your first steps into the world of programming. We’ve taken two of the most powerful and versatile…

Getting Started with Python Your First Code Essentially, you’ve already written your first piece of code with the ‘print(“Hello everyone!”)’ function from the previous tutorial. However, let’s expand that and look at entering your code and playing around with some other Python examples. 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.…

Getting Started with Python User Input We’ve seen some basic user interaction with the code from a few of the examples earlier, so now would be a good time to focus solely on how you would get information from the user then store and present it. 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…

Working with Data Tuples Tuples are very much identical to lists. However, where lists can be updated, deleted or changed in some way, a tuple remains a constant. This is called immutable and they’re perfect for storing fixed data items. 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,…

Working with Data Formatting Strings When you work with data, creating lists, dictionaries and objects you may often want to print out the results. Merging strings with data is easy especially with Python 3, as earlier versions of Python tended to complicate matters. 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…

Working with Data Writing to Files The ability to read external files within Python is certainly handy but writing to a file is better still. Using the write() function, you’re able to output the results of a program to a file, that you can then read() back into Python. 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…

Using Modules Calendar Module Beyond the time module, the calendar module can produce some interesting results when executed within your code. It does far more than simply display the date in the time module-like format, you can actually call up a wall calendar type display. 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 2017 are displayed in a wall calendar fashion. Naturally…

Using Modules Tkinter Module While running your code from the command line, or even in the Shell, is perfectly fine, Python is capable of so much more. The Tkinter module enables the programmer to set up a Graphical User Interface to interact with the user, and it’s surprisingly powerful too. 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,…

C++ Input/Output File Input/Output The standard iostream library provides C++ coders with the cin and cout input and output functionality. However, to be able to read and write from a file you need to utilise another C++ library, called fstream. 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…

Loops and Decision Making Do… While Loop A do… while loop differs slightly from that of a for or even a while loop. Both for and while set and examine the state of the condition at the start of the loop, or the top of the loop if you prefer. However, a do… while loop, is similar to a while loop but instead checks the condition at the bottom of the loop. 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:…

Working with Code Common Coding Mistakes When you start something new you’re inevitably going to make mistakes, this is purely down to inexperience and those mistakes are great teachers in themselves. However, even experts make the occasional mishap. Thing is, to learn from them as best you can. X=MISTAKE, PRINT Y There are many pitfalls for the programmer to be aware of, far too many to be listed here. Being able to recognise a mistake and fix it is when you start to move into more advanced territory. SMALL CHUNKS It would be wonderful to be able to work like Neo from The Matrix movies. Simply ask, your operator loads it into your memory and you instantly know everything about the subject. Sadly though, we can’t do that. The first…

Say Hello to Python Getting to Know Python Python is the greatest computer programming language ever created. It enables you to fully harness the power of a computer, in a language that’s clean and easy to understand. 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…

Getting Started with Python Using Comments When writing your code, the flow of it, what each variable does, how the overall program will operate and so on is all inside your head. Another programmer could follow the code line by line but over time, it can become difficult to read. #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,…

Working with Data Dictionaries Lists are extremely useful but dictionaries in Python are by far the more technical way of dealing with data items. They can be tricky to get to grips with at first but you’ll soon be able to apply them to your own code. 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…

Working with Data Date and Time When working with data it’s often handy to have access to the time. For example, you may want to time-stamp an entry or see at what time a user logged into the system and for how long. Luckily acquiring the date and time is easy, thanks to the Time module. 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:…

Using Modules OS Module The OS module allows you to interact directly with the built-in commands found in your operating system. Commands vary depending on the OS you’re running, as some will work with Windows whereas others will work with Linux and macOS. 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…

Using Modules Pygame Module We’ve had a brief look at the Pygame module already but there’s a lot more to it that needs exploring. Pygame was developed to help Python programmers create either graphical or text-based games. 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,…

C++ Fundamentals Using Comments While comments may seem like a minor element to the many lines of code that combine to make a game, application or even an entire operating system, in actual fact they’re probably one of the most important factors. THE IMPORTANCE OF COMMENTING Comments inside code are basically human readable descriptions that detail what the code is doing at that particular point. They don’t sound especially important but code without comments is one of the many frustrating areas of programming, regardless of whether you’re a professional or just starting out. In short, all code should be commented in such a manner as to effectively describe the purpose of a line, section, or individual elements. You should get in to the habit of commenting as much as possible,…

C++ Fundamentals Strings Strings are objects that represent and hold sequences of characters. For example, you could have a universal greeting in your code ‘Welcome’ and assign that as a string to be called up wherever you like in the program. 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.…

C++ Input/Output Character Literals In C++ a literal is an object or variable that once defined remains the same throughout the code. However, a character literal is defined by a backslash, such as the \n you’ve been using at the end of a cout statement to signify a new line. 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…

Loops and Decision Making While Loop 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.…

Loops and Decision Making If Statement The decision making statement ‘if’ is probably one of the most used statements in any programming language, regardless of whether it’s C++, Python, BASIC or anything else. It represents a junction in the code, where IF one condition is true, do this; or IF it’s false, do that. 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…

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Getting Started with Python Conditions and Loops Conditions and loops are what makes a program interesting; they can be simple or rather complex. How you use them depends greatly on what the program is trying to achieve; they could be the number of lives left in a game or just displaying a countdown. 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…

Working with Data Lists Lists are one of the most common types of data structures you will comes across in Python. A list is simply a collection of items, or data if you prefer, that can be accessed as a whole, or individually if wanted. 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…

Working with Data Splitting and Joining Strings When dealing with data in Python, especially from a user’s input, you will undoubtedly come across long sets of strings. A useful skill to learn in Python programming is being able to split those long strings for better readability. 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…

Working with Data Python Graphics While dealing with text on the screen, either as a game or in a program, is great, there will come a time when a bit of graphical representation wouldn’t go amiss. Python 3 has numerous ways in which to include graphics and they’re surprisingly powerful too. 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…

Using Modules Random Module The random module is one you will likely come across many times in your Python programming lifetime; as the name suggests, it’s designed to create random numbers or letters. However, it’s not exactly random but it will suffice for most needs. 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…

Using Modules Create Your Own Modules Large programs can be much easier to manage if you break them up into smaller parts and import the parts you need as modules. Learning to build your own modules also makes it easier to understand how they work. 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…

C++ Fundamentals Structure of a C++ Program C++ has a very defined structure and way of doing things. Miss something out, even as small as a semicolon, and your entire program will fail to be compiled and executed. Many a professional programmer has fallen foul of sloppy structure. #INCLUDE <C++ STRUCTURE> Learning the basics of programming, you begin to understand the structure of a program. The commands may be different from one language to the next, but you will start to see how the code works. C++ C++ was invented by Danish student Bjarne Stroustrup in 1979, as a part of his Ph.D. thesis. Initially C++ was called C with Classes, which added features to the already popular C programming language, while making it a more user-friendly environment through a…

C++ Fundamentals Variables Variables differ slightly when using C++ as opposed to Python. In Python, you can simply state that ‘a’ equals 10 and a variable is assigned. However, in C++ a variable has to be declared with its type before it can be used. 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…

C++ Input/Output Defining Constants Constants are fixed values in your code. They can be any basic data type but as the name suggests their value remains constant throughout the entire code. There are two separate ways to define a constant in C++, the #define pre-processor and const. #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…

Loops and Decision Making For Loop In some respects, a for loop works in a very similar way to that of a while loop, although it’s structure is different. A for loop is split into three stages: an initialiser, a condition and an incremental step. Once set up, the loop repeats itself until the condition becomes false. 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…

Loops and Decision Making If… Else Statement There is a much better way to use an if statement in your code, with if… else. If… else works in much the same way as a standard if statement. If the Boolean expression is true, the code with in the braces is executed. Else, the code within the next set of braces is used instead. 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…