Innholdsfortegnelse for The Python Book 16th Edition i The Python Book

Basics 01 Running Python scripts On most of the UNIX systems, you can run Python scripts from the command line. 02 Running Python programs from interpreter The Python interactive interpreter makes it easy to try your first steps in programming and using all Python commands. You just issue each command at the command prompt (>>>), one by one, and the answer is immediate. Python interpreter can be started by issuing the command: In this article, all the code starting at the >>> symbol is meant to be given at the Python prompt. It is also important to remember that Python takes tabs very seriously – so if you are receiving any error that mentions tabs, correct the tab spacing. 03 Dynamic typing In Java, C++, and other statically typed languages, you…

So you’ve learnt how to program rock, paper, scissors and guessed your way to victory at hangman. Now it’s time to head to Las Vegas and play our cards right. Or in this case, virtual dice, as we continue with our Python game tutorials and introduce you to some poker dice. We’re again using some of the lessons we’ve already learnt, including random number generation, list creation and modification, human input, rule setting, scoring and more. But we’ll also be adding some new skills in this tutorial. Namely, we’ll be creating and appending lists with random numbers, and using functions multiple times in one block of code to cut down on bloat. Again, we recommend using IDLE, and we’re using Python 2 to ensure compatibility with a wider variety of…

Here we’ll be implementing an instant messenger in Python with a client-server architecture. This means each client connects to the server, which relays any message that one client sends to all other clients. The server will also notify the other clients when someone joins or leaves the server. The instant messenger can work anywhere a TCP socket can: on the same computer with the loopback interface, across various computers on a LAN, or even over the internet if you were to configure your router correctly. However, our messages aren’t encrypted, so we wouldn’t recommend that. Writing an instant messenger is an interesting technical problem that covers a bunch of areas that you may not have come across while programming before: • We’ll be employing sockets, which are used to transmit data…

In the main article, we have only looked at how to connect to an email server and how to read from it. But what if you need to be able to also send emails using code? Similar to poplib and imaplib, the Python standard library includes a module called smtplib. Again, similar to poplib and imaplib, you need to create an SMTP object for the connection, and then log in to the server. If you’re using the GMail SMTP server, you could use the code This code asks the end user for their password, but if you aren’t concerned about security, you could have it hard-coded into the code. Also, you only need to use the login() method for those servers that require it. If you are running your own…

The code Download from linuxformat.com/archives Pac-Man is arguably one of the most famous video game characters in the world. First shooting to fame in 1980 with the release of the arcade version, Pac-Man has seen many iterations, remakes and sequels over the years, but nothing compares to the original. It’s a simple premise, really. Pac-Man is a yellow, disk-shaped, mainly feature-less character, who roams around a 2D environment collecting dots. The player has to collect all the dots in the room without being touched by any of the four enemy characters in the form of ghosts. Pinky, Blinky, Inky and Clyde are brightly coloured to stand out against the black background, being pink, red, cyan and orange, respectively. Pac-Man must avoid the ghosts and collect all the dots to progress…

This series of building retro games in Python has so far seen us coding a lunar landing space module (LXF262), a side-scrolling platformer (LXF263), the famous pellet-munching, ghost-chasing Pac-Man (page 104), and in this tutorial we’re going to develop our own version of Pong! To many, Pong is the original arcade game. It’s certainly the first video game to become a commercial success. Released for arcades in 1972 and for the home in 1975, Pong has gained popularity worldwide and is now permanently memorialised in the Smithsonian Institute in Washingon, DC. Developed and self-published by Atari, Pong is a 2D table tennis simulation with arguably the most simplistic game design imaginable, while managing to achieve an incredibly addictive gaming experience. What gameplay? Gameplay mechanics in Pong are quite simple. It’s…

We had great fun creating our basic Space Invaders clone, Pivaders, for the previous tutorial. One of the key challenges with the project was keeping it to a manageable size – just 300 lines of Python. Without the use of Pygame’s strong set of features, that goal would likely have been overshot at least twofold. Pygame’s ability to group, manage and detect collisions thanks to the Sprite class really made a great difference to our project, not just in terms of length but in simplicity. If you missed the first part of the project, you can find the v0.1 code listing on GitHub via git.io/cBVTBg, while you can find version v0.2, including all the images, music and sound effects we used, over at git.io/8QsK-w. Even working within the clearly defined…

Python and Flask are a great combination when you’re looking to handle the Twitter OAuth process and build requests to obtain tokens. We’ve used Twitter here because of the large amount of easily digestible data available on it. However, since Twitter adheres to the standards set out by OAuth 1.0, the code we’ve used to sign and build requests can be modified to work with any third-party API using the same standard without a great deal of work. For years PHP has been a mainstay of template generation, but now with well-documented frameworks such as Flask, Sinatra and Handlebars, the ability to use powerful scripting languages greatly improves our ability to make great web services. Here, we’re going to use Python, Flask and its templating engine to display tweets. Flask…

We’ve been building our Django blog to create and display posts, allow people to make comments, and filter posts by month like a classic blog sidebar. We still have a bit of a way to go until it looks and behaves more like a classic blog, though. In this tutorial, we’re going to add in summaries, excerpts, categories and finally an RSS feed. This allows us to look at a few things – firstly we’ll get a better understanding of cross-model referencing and how that works in the admin site. We will also go through how to make changes to the database, and how Django helps when creating an SQL query. Finally, the RSS feed is part of a standard feed library in Django itself. We will learn how to…

Combining an old toy and a Raspberry Pi, you can embed a selection of components to create your own augmented toy that responds to user input. For example, take a £3 R2-D2 sweet dispenser, light it up, play music and stream a live web feed to your mobile device. Part one of this two-part tutorial covers setting up four basic features: an LED for the eye, a haptic motor to simulate an electric shock, a webcam stream from a hidden camera and the Star Wars theme tune broadcast to a radio. You may choose to combine these with your own hacks or use them as standalone features in other projects. Don’t feel limited to just using a Star Wars toy either – we used the R2D2 figure because it was…

Python is a great programming language for both beginners and experts. It is designed with code readability in mind, making it an excellent choice for beginners who are still getting used to various programming concepts. The language is popular and has plenty of libraries available, allowing programmers to get a lot done with relatively little code. You can make all kinds of applications in Python: you could use the Pygame framework to write simple 2D games, you could use the GTK libraries to create a windowed application, or you could try something a little more ambitious like an app such as creating one using Python’s Bluetooth and Input libraries to capture the input from a USB keyboard and relay the input events to an Android phone. For this guide we’re…

This tutorial will guide you through making a rock, paper, scissors game in Python. The code applies the lessons from the masterclass – and expands on what was included there – and doesn’t require any extra Python modules to run, like Pygame. Rock, paper, scissors is the perfect game to show off a little more about what exactly Python can do. Human input, comparisons, random selections and a whole host of loops are used in making a working version of the game. It’s also easy enough to adapt and expand as you see fit, adding rules and results, and even making a rudimentary AI if you wish. For this particular tutorial, we also recommend using IDLE. IDLE is a great Python IDE that is easily obtainable in most Linux distributions…

The three basic games we have made in Python so far have all run in the command line or via IDLE, a Python IDE. While this allowed us to show off different ways to use Python code, we haven’t actually shown you how to present it yet. In this tutorial, we will take all three games and put them all into one neatly unified graphical interface. To this end, we’ll be making use of the small line of code we added at the bottom of each previous tutorial so we can import them as modules into our main graphical script. We’ll also modify the existing code to add some graphical elements. To do all this we’ll be using Tkinter, a default module available in Python that allows you to create…

For a lot of scientific problems, you need to play with your data in an interactive way. The original way you would do this was to use the Ipython web notebook. This project has since been renamed Jupyter. For those who have used a program like Mathematica or Maple, the interface should seem very familiar. Jupyter starts a server process, by default on port 8888, and then will open a web browser where you can open a worksheet. Like most other programs of this type, the entries run in chronological order, not in the order that they happen on the worksheet. This can be a bit confusing at first, but it means that if you go to edit an earlier entry, all of the following entries need to be re-executed…

Kodi (formerly XBMC) is perhaps the most important thing that has ever happened in the open source media centre space. It started its life on the original Xbox videogames console and since then it has become the de facto software for multimedia aficionados. It also has been forked into many other successful media centre applications such as Boxee and Plex. Kodi has ultimately grown into a very powerful open source application with a solid community behind it. It supports almost all major platforms, including different hardware architectures. It is available for Linux, Windows, mac OS , Android, iOS and Raspberry Pi. In these pages we will learn to build extensions for Kodi. Extensions are a way of adding features to Kodi without having to learn the core of XBMC or…

The average software project today relies on dozens – sometimes hundreds – of open source libraries. Are those libraries up to date? Are there any security vulnerabilities in the versions you’re using? How would you even know? SourceClear makes it easy to answer these questions and more, automatically. You’ll get complete analysis of your open-source dependencies – security vulnerabilities, out-of-date libraries, and license reports. To analyse your project, we’ll be using the SourceClear command-line agent. By tapping into the native build and package managers that manage open-source dependencies, we’ll start by gathering information on the full dependency graph. We’ll then match up those libraries to the SourceClear Registry – the largest database in the world of open source security vulnerabilities – and help you triage the issues we might find.…

Each Linux file has permissions associated with it. Look at the following output: The first column of the previous output of the ls command shows the permissions of each file. As you can see, the permissions of each file take 10 places, which can also be viewed as bits. Apart from the first bit, which is defined by Linux and declares the type of the entry, the remaining nine places can be collected into three groups with each one having three bits. The first set explains the permissions of the user, the second set is about the permissions of the main Linux group the user belongs to, and the last part is about the permissions of the rest of the users. If you’re familiar with binary arithmetic, it’s easy to…

With Pong having been around for over 40 years, we’ve seen many iterations of what is essentially quite a basic game. Once our PyGame version of the game is fully functional, perhaps we could consider what steps we might take to improve our game? On the easier end of the spectrum we could change the colour scheme from black and white to something more contemporary. When Pong was first released, black and white were the only options available. By the time the Atari came out there were 128 colours in the PAL format. Eight-bit consoles introduced 256 colours, and we’re now literally in the billions. Our game is designed in a VGA resolution, so if we were sticking to those retro/vintage aesthetics we’d only have 16 colours available to us.…

You may remember or have even played the classic Minesweeper PC game that originally dates back to the 60s. Over the years it has been bundled with most operating systems, appeared on mobile phones, and even featured as a mini-game variation on Super Mario Bros. This project will walk you through how to create a simple version in Minecraft: it’s Minecraft Minesweeper! You will code a program that sets out an arena of blocks and turns one of these blocks into a mine. To play the game, guide your player around the board. Each time you stand on a block you turn it to gold and collect points, but watch out for the mine as it will end the game and cover you in lava! 01 Update and install To…

Django djangoproject.com GOOD FOR: Large database-driven web apps with multiuser support and sites that need to have heavily customisable admin interfaces Django contains a lot of impressive features, all in the name of interfaces and modules. These include autowiring, admin interfaces and database migration management tools by default for all of your projects and applications. Django will help to enable rapid application development for enterprise-level projects, whilst also enabling a clear modular reuseable approach to code using subapplications. Flask flask.pocoo.org GOOD FOR: Creating full-featured RESTful APIs. Its ability to manage multiple routes and methods is very impressive Flask’s aim is to provide a set of commonly used components such as URL routing and templates. Flask will also work on controlling the request and response objects, all-in-all this means it is…

Creating your own blog always feels like a great accomplishment. Sure, you could use the fantastic WordPress if you need a complete blog with every feature you’d ever need right now. And Tumblr exists for people who just want to write something, or post pictures of corgis in space. You don’t have full control from start to finish with a prefabricated blog, though, and neither of these is written in the fantastic Django. Django is of course based on Python, the object-orientated programming language designed to have clearly readable syntax. Due to its Python base, it’s an incredibly powerful and simple-to-use language for web development with a vast array of applications. So let’s use it to make a blog. In this first section of the process we will explore how…

News is everywhere. We are constantly bombarded with news stories via mobile devices, tablets, laptops, TVs and radios. You probably also overhear people discussing news stories. Traditionally the type of newspaper that you read was used to indicate what type of person you were – a kind of litmus test of your income, political views, social status and where your ethics and morals are aligned. For example, an article by IBT in 2013 found that 40 per cent of readers of the New Yorker were making more than $75,000 (approximately £59,000) a year. Nowadays, the news caters for every taste with variations such as gossip, detailed, statistical analysis, photographic and so many more. Then there is ‘fake news’, which is by no means a modern concept – its roots go…

We have now created a simple selector for the trio of Python games we made previously. This interface was able to launch a GUI for our rock, paper, scissors game, and run the other two in the terminal. Now, we’re going to convert the hangman and poker dice codes to work in a similar way to rock, paper, scissors. The trick with hangman comes in allowing for a different type of input, text, and the ability to have multiple rounds of the game. Tkinter allows for text entry, and we rely a lot less on ‘while’ loops to play the game in its entirety. Poker Dice needs to keep the dice analysis code, and the option to change specific dice using checkboxes. We’ll be modifying a large amount of the…

Robotics is the most direct way that your code can interact with the world around you. It can read actual sensor information and move real actuators and get real work done. The first thing your robot needs is the ability to sense the world around it. The one sense that we as humans feel is most useful is sight. With web cameras being so cheap and easy to connect to hardware, vision is easy to give to your robot. The real problem is how to interpret this data. Luckily, you can use the OpenCV project to do just that. It is a vision package that can provide simple image gathering and processing, to extremely complex functions like face recognition and extraction of 3D objects. You can identify and track objects…

NumPy is the primary Python package for performing scientific computing. It has a powerful N-dimensional array object, tools for integrating C/C++ and Fortran code, linear algebra, Fourier transform, and random number capabilities, among other things. NumPy also supports broadcasting, which is a clever way for universal functions to deal in a meaningful way with inputs that do not have exactly the same form. Apart from its capabilities, the other advantage of NumPy is that it can be integrated into Python programs. In other words, you may get your data from a database, the output of another program, an external file or an HTML page and then process it using NumPy. This article will show you how to install NumPy, make calculations, plot data, read and write external files, and it…

When you’re learning to program in a new language or trying to master a new module, experimenting with a familiar and relatively simple project is a very useful exercise to help expand your understanding of the tools you’re using. Our Space Invaders clone is one such example that lends itself perfectly to Python and the Pygame module – it’s a simple game with almost universally understood rules and logic. While the Invaders meander their way down the screen towards you, it’s your job to pick them off while dodging their random fire. When one wave is conquered, another faster, more aggressive wave appears. We’ve tried to use many features of Pygame, which is designed to make the creation of games and interactive applications easier. We’ve extensively used the Sprite class,…

Games are a great way of understanding a language: you have a goal to work towards, and each feature you add brings more fun. However, games need libraries and modules for graphics and other essential games features. While the Pygame library made it relatively easy to make games in Python, it still brings in boilerplate code that you need before you get started – barriers to you or your kids getting started in coding. Pygame Zero deals with all of this boilerplate code for you, aiming to get you coding games instantly. Pg0 (as we’ll abbreviate it) makes sensible assumptions about what you’ll need for a game – from the size of the window to importing the game library – so that you can get straight down to coding your…

01 Install Flask Create a new directory inside of which your project will live. Open a Terminal window and navigate to be inside your new directory. Create a new virtual environment for this project, placed inside a new directory called ‘venv’, and activate it. Once inside the new virtual shell, proceed to installing Flask using the ‘pip install Flask’ command. 02 Create Index Create a new file in the root of the project location called ‘index.py’. The sample API will use a SQLite database, so we need to import that module for use in the application. We’ll also import some core components from the Flask module to handle request management and response formatting as well as some other functions. The minimum import for a Flask application is Flask itself. 03…

Heroku heroku.com This app is perhaps one of the most well-known cloud hosting providers. Their stack server environments support a number of core web app languages including Python as standard. Their unique Toolbelt command-line features and integration with Git repositories, as well as being incredibly quick and easy to scale and improve performance, makes them an obvious choice. A free account will let you run a Python web app on one dyno instance without any cost. Python Anywhere www.pythonanywhere.com Another hosted option, and one created specifically for Python applications in general is Python Anywhere. The free basic option plan has enough weight and power behind it to get you up and running with a Python web app without having to scale, but as soon as your project gains traction, you…

In the last tutorial we began to build the most basic of blogs, and learned how to use a bit of Django in the process. We can now set up a new project, create a database and write basic code to read and write to the database. All simple stuff, but of course it’s core to building websites where Django might be called upon. Here we will give the front end of the site an overhaul, making it more of the standard you would expect from a modern blog. This will include a sidebar, pages, post pages and the ability to add and moderate comments. In the process we will learn some more of the benefits that come with using Django to develop websites. You should keep using Django 4…

This tutorial combines the Maplin Robotic Arm and Pimoroni’s Skywriter HAT to enable you to take control of the robot with just the touch of your fingertips. The arm can move through three points of articulation and ends in a clamp to give you maximum flexibility with movement. The arm also moves through 120 degrees in the wrist, 300 degrees at the elbow, 180 degrees at the base in the vertical and 270 degrees in the horizontal. It is easy to assemble and is a great beginners’ robot. In this tutorial you will first install the Python modules to enable your Raspberry Pi to interact with the USB port, and then learn how to use Python code to send commands to and receive them from the arm. Next we’ll write…

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