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<section id="revision-pygame-fundamentals">
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<section id="makegames-2">
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<span id="id1"></span><h2>2. Revision: Pygame fundamentals<a class="headerlink" href="#makegames-2" title="Permalink to this headline">¶</a></h2>
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<section id="the-basic-pygame-game">
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<span id="makegames-2-1"></span><h3>2.1. The basic Pygame game<a class="headerlink" href="#the-basic-pygame-game" title="Permalink to this headline">¶</a></h3>
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<p>For the sake of revision, and to ensure that you are familiar with the basic structure of a Pygame program, I'll briefly run through
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a basic Pygame program, which will display no more than a window with some text in it, that should, by the end, look something like
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this (though of course the window decoration will probably be different on your system):</p>
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<img alt="../_images/tom_basic.png" src="../_images/tom_basic.png" />
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<p>The full code for this example looks like this:</p>
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<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/python</span>
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<span class="kn">import</span> <span class="nn">pygame</span>
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<span class="kn">from</span> <span class="nn">pygame.locals</span> <span class="kn">import</span> <span class="o">*</span>
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<span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
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<span class="c1"># Initialise screen</span>
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<span class="n">pygame</span><span class="o">.</span><span class="n">init</span><span class="p">()</span>
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<span class="n">screen</span> <span class="o">=</span> <span class="n">pygame</span><span class="o">.</span><span class="n">display</span><span class="o">.</span><span class="n">set_mode</span><span class="p">((</span><span class="mi">150</span><span class="p">,</span> <span class="mi">50</span><span class="p">))</span>
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<span class="n">pygame</span><span class="o">.</span><span class="n">display</span><span class="o">.</span><span class="n">set_caption</span><span class="p">(</span><span class="s1">'Basic Pygame program'</span><span class="p">)</span>
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<span class="c1"># Fill background</span>
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<span class="n">background</span> <span class="o">=</span> <span class="n">pygame</span><span class="o">.</span><span class="n">Surface</span><span class="p">(</span><span class="n">screen</span><span class="o">.</span><span class="n">get_size</span><span class="p">())</span>
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<span class="n">background</span> <span class="o">=</span> <span class="n">background</span><span class="o">.</span><span class="n">convert</span><span class="p">()</span>
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<span class="n">background</span><span class="o">.</span><span class="n">fill</span><span class="p">((</span><span class="mi">250</span><span class="p">,</span> <span class="mi">250</span><span class="p">,</span> <span class="mi">250</span><span class="p">))</span>
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<span class="c1"># Display some text</span>
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<span class="n">font</span> <span class="o">=</span> <span class="n">pygame</span><span class="o">.</span><span class="n">font</span><span class="o">.</span><span class="n">Font</span><span class="p">(</span><span class="kc">None</span><span class="p">,</span> <span class="mi">36</span><span class="p">)</span>
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<span class="n">text</span> <span class="o">=</span> <span class="n">font</span><span class="o">.</span><span class="n">render</span><span class="p">(</span><span class="s2">"Hello There"</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">10</span><span class="p">))</span>
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<span class="n">textpos</span> <span class="o">=</span> <span class="n">text</span><span class="o">.</span><span class="n">get_rect</span><span class="p">()</span>
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<span class="n">textpos</span><span class="o">.</span><span class="n">centerx</span> <span class="o">=</span> <span class="n">background</span><span class="o">.</span><span class="n">get_rect</span><span class="p">()</span><span class="o">.</span><span class="n">centerx</span>
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<span class="n">background</span><span class="o">.</span><span class="n">blit</span><span class="p">(</span><span class="n">text</span><span class="p">,</span> <span class="n">textpos</span><span class="p">)</span>
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<span class="c1"># Blit everything to the screen</span>
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<span class="n">screen</span><span class="o">.</span><span class="n">blit</span><span class="p">(</span><span class="n">background</span><span class="p">,</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">))</span>
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<span class="n">pygame</span><span class="o">.</span><span class="n">display</span><span class="o">.</span><span class="n">flip</span><span class="p">()</span>
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<span class="c1"># Event loop</span>
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<span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
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<span class="k">for</span> <span class="n">event</span> <span class="ow">in</span> <span class="n">pygame</span><span class="o">.</span><span class="n">event</span><span class="o">.</span><span class="n">get</span><span class="p">():</span>
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<span class="k">if</span> <span class="n">event</span><span class="o">.</span><span class="n">type</span> <span class="o">==</span> <span class="n">QUIT</span><span class="p">:</span>
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<span class="k">return</span>
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<span class="n">screen</span><span class="o">.</span><span class="n">blit</span><span class="p">(</span><span class="n">background</span><span class="p">,</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">))</span>
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<span class="n">pygame</span><span class="o">.</span><span class="n">display</span><span class="o">.</span><span class="n">flip</span><span class="p">()</span>
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<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s1">'__main__'</span><span class="p">:</span> <span class="n">main</span><span class="p">()</span>
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</pre></div>
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</div>
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</section>
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<section id="basic-pygame-objects">
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<span id="makegames-2-2"></span><h3>2.2. Basic Pygame objects<a class="headerlink" href="#basic-pygame-objects" title="Permalink to this headline">¶</a></h3>
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<p>As you can see, the code consists of three main objects: the screen, the background, and the text. Each of these objects is created
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by first calling an instance of an in-built Pygame object, and then modifying it to fit our needs. The screen is a slightly special
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case, because we still modify the display through Pygame calls, rather than calling methods belonging to the screen object. But for
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all other Pygame objects, we first create the object as a copy of a Pygame object, giving it some attributes, and build our game
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objects from them.</p>
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<p>With the background, we first create a Pygame Surface object, and make it the size of the screen. We then perform the convert()
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operation to convert the Surface to a single pixel format. This is more obviously necessary when we have several images and surfaces,
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all of different pixel formats, which makes rendering them quite slow. By converting all the surfaces, we can drastically speed up
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rendering times. Finally, we fill the background surface with white (255, 255, 255). These values are <em class="firstterm">RGB</em> (Red Green
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Blue), and can be worked out from any good paint program.</p>
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<p>With the text, we require more than one object. First, we create a font object, which defines which font to use, and the size of the
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font. Then we create a text object, by using the <code class="docutils literal notranslate"><span class="pre">render</span></code> method that belongs to our font object, supplying three arguments:
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the text to be rendered, whether or not it should be anti-aliased (1=yes, 0=no), and the color of the text (again in RGB format). Next
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we create a third text object, which gets the rectangle for the text. The easiest way to understand this is to imagine drawing a
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rectangle that will surround all of the text; you can then use this rectangle to get/set the position of the text on the screen. So
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in this example we get the rectangle, set its <code class="docutils literal notranslate"><span class="pre">centerx</span></code> attribute to be the <code class="docutils literal notranslate"><span class="pre">centerx</span></code> attribute of the
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background (so the text's center will be the same as the background's center, i.e. the text will be centered on the screen on the x
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axis). We could also set the y coordinate, but it's not any different so I left the text at the top of the screen. As the screen is
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small anyway, it didn't seem necessary.</p>
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</section>
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<section id="blitting">
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<span id="makegames-2-3"></span><h3>2.3. Blitting<a class="headerlink" href="#blitting" title="Permalink to this headline">¶</a></h3>
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<p>Now we have created our game objects, we need to actually render them. If we didn't and we ran the program, we'd just see a
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blank window, and the objects would remain invisible. The term used for rendering objects is <em class="firstterm">blitting</em>, which is where
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you copy the pixels belonging to said object onto the destination object. So to render the background object, you blit it onto the
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screen. In this example, to make things simple, we blit the text onto the background (so the background will now have a copy of the
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text on it), and then blit the background onto the screen.</p>
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<p>Blitting is one of the slowest operations in any game, so you need to be careful not to blit too much onto the screen in every frame.
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If you have a background image, and a ball flying around the screen, then you could blit the background and then the ball in every
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frame, which would cover up the ball's previous position and render the new ball, but this would be pretty slow. A better solution is
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to blit the background onto the area that the ball previously occupied, which can be found by the ball's previous rectangle, and then
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blitting the ball, so that you are only blitting two small areas.</p>
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</section>
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<section id="the-event-loop">
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<span id="makegames-2-4"></span><h3>2.4. The event loop<a class="headerlink" href="#the-event-loop" title="Permalink to this headline">¶</a></h3>
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<p>Once you've set the game up, you need to put it into a loop so that it will continuously run until the user signals that he/she wants
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to exit. So you start an open <code class="docutils literal notranslate"><span class="pre">while</span></code> loop, and then for each iteration of the loop, which will be each frame of the game,
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update the game. The first thing is to check for any Pygame events, which will be the user hitting the keyboard, clicking a mouse
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button, moving a joystick, resizing the window, or trying to close it. In this case, we simply want to watch out for for user trying
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to quit the game by closing the window, in which case the game should <code class="docutils literal notranslate"><span class="pre">return</span></code>, which will end the <code class="docutils literal notranslate"><span class="pre">while</span></code> loop.
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Then we simply need to re-blit the background, and flip (update) the display to have everything drawn. OK, as nothing moves or happens
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in this example, we don't strictly speaking need to re-blit the background in every iteration, but I put it in because when things are
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moving around on the screen, you will need to do all your blitting here.</p>
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</section>
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<section id="ta-da">
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<span id="makegames-2-5"></span><h3>2.5. Ta-da!<a class="headerlink" href="#ta-da" title="Permalink to this headline">¶</a></h3>
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<p>And that's it - your most basic Pygame game! All games will take a form similar to this, but with lots more code for the actual game
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functions themselves, which are more to do your with programming, and less guided in structure by the workings of Pygame. This is what
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this tutorial is really about, and will now go onto.</p>
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</section>
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</section>
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</section>
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<br /><br />
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<hr />
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<a href="https://github.com/pygame/pygame/edit/main/docs/reST/tut\tom_games2.rst" rel="nofollow">Edit on GitHub</a>
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<div class="clearer"></div>
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</div>
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</div>
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<h3>Navigation</h3>
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accesskey="I">index</a></li>
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accesskey="N">next</a> |</li>
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<li class="nav-item nav-item-0"><a href="../index.html">pygame v2.5.2 documentation</a> »</li>
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