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<li class="nav-item nav-item-0"><a href="index.html">Evennia 0.9.5</a> &#187;</li>
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<section class="tex2jax_ignore mathjax_ignore" id="debugging">
<h1>Debugging<a class="headerlink" href="#debugging" title="Permalink to this headline"></a></h1>
<p>Sometimes, an error is not trivial to resolve. A few simple <code class="docutils literal notranslate"><span class="pre">print</span></code> statements is not enough to find
the cause of the issue. Running a <em>debugger</em> can then be very helpful and save a lot of time.
Debugging
means running Evennia under control of a special <em>debugger</em> program. This allows you to stop the
action at a given point, view the current state and step forward through the program to see how its
logic works.</p>
<p>Evennia natively supports these debuggers:</p>
<ul class="simple">
<li><p><a class="reference external" href="https://docs.python.org/2/library/pdb.html">Pdb</a> is a part of the Python distribution and
available out-of-the-box.</p></li>
<li><p><a class="reference external" href="https://pypi.org/project/pudb/">PuDB</a> is a third-party debugger that has a slightly more
‘graphical’, curses-based user interface than pdb. It is installed with <code class="docutils literal notranslate"><span class="pre">pip</span> <span class="pre">install</span> <span class="pre">pudb</span></code>.</p></li>
</ul>
<section id="debugging-evennia">
<h2>Debugging Evennia<a class="headerlink" href="#debugging-evennia" title="Permalink to this headline"></a></h2>
<p>To run Evennia with the debugger, follow these steps:</p>
<ol>
<li><p>Find the point in the code where you want to have more insight. Add the following line at that
point.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">set_trace</span><span class="p">;</span><span class="n">set_trace</span><span class="p">()</span>
</pre></div>
</div>
</li>
<li><p>(Re-)start Evennia in interactive (foreground) mode with <code class="docutils literal notranslate"><span class="pre">evennia</span> <span class="pre">istart</span></code>. This is important -
without this step the debugger will not start correctly - it will start in this interactive
terminal.</p></li>
<li><p>Perform the steps that will trigger the line where you added the <code class="docutils literal notranslate"><span class="pre">set_trace()</span></code> call. The debugger
will start in the terminal from which Evennia was interactively started.</p></li>
</ol>
<p>The <code class="docutils literal notranslate"><span class="pre">evennia.set_trace</span></code> function takes the following arguments:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span> <span class="n">evennia</span><span class="o">.</span><span class="n">set_trace</span><span class="p">(</span><span class="n">debugger</span><span class="o">=</span><span class="s1">&#39;auto&#39;</span><span class="p">,</span> <span class="n">term_size</span><span class="o">=</span><span class="p">(</span><span class="mi">140</span><span class="p">,</span> <span class="mi">40</span><span class="p">))</span>
</pre></div>
</div>
<p>Here, <code class="docutils literal notranslate"><span class="pre">debugger</span></code> is one of <code class="docutils literal notranslate"><span class="pre">pdb</span></code>, <code class="docutils literal notranslate"><span class="pre">pudb</span></code> or <code class="docutils literal notranslate"><span class="pre">auto</span></code>. If <code class="docutils literal notranslate"><span class="pre">auto</span></code>, use <code class="docutils literal notranslate"><span class="pre">pudb</span></code> if available, otherwise
use <code class="docutils literal notranslate"><span class="pre">pdb</span></code>. The <code class="docutils literal notranslate"><span class="pre">term_size</span></code> tuple sets the viewport size for <code class="docutils literal notranslate"><span class="pre">pudb</span></code> only (it’s ignored by <code class="docutils literal notranslate"><span class="pre">pdb</span></code>).</p>
</section>
<section id="a-simple-example-using-pdb">
<h2>A simple example using pdb<a class="headerlink" href="#a-simple-example-using-pdb" title="Permalink to this headline"></a></h2>
<p>The debugger is useful in different cases, but to begin with, let’s see it working in a command.
Add the following test command (which has a range of deliberate errors) and also add it to your
default cmdset. Then restart Evennia in interactive mode with <code class="docutils literal notranslate"><span class="pre">evennia</span> <span class="pre">istart</span></code>.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="c1"># In file commands/command.py</span>
<span class="k">class</span> <span class="nc">CmdTest</span><span class="p">(</span><span class="n">Command</span><span class="p">):</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="sd"> A test command just to test pdb.</span>
<span class="sd"> Usage:</span>
<span class="sd"> test</span>
<span class="sd"> &quot;&quot;&quot;</span>
<span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;test&quot;</span>
<span class="k">def</span> <span class="nf">func</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">set_trace</span><span class="p">;</span> <span class="n">set_trace</span><span class="p">()</span> <span class="c1"># &lt;--- start of debugger</span>
<span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You&#39;ve found </span><span class="si">{}</span><span class="s2">.&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">obj</span><span class="o">.</span><span class="n">get_display_name</span><span class="p">()))</span>
</pre></div>
</div>
<p>If you type <code class="docutils literal notranslate"><span class="pre">test</span></code> in your game, everything will freeze. You won’t get any feedback from the game,
and you won’t be able to enter any command (nor anyone else). It’s because the debugger has started
in your console, and you will find it here. Below is an example with <code class="docutils literal notranslate"><span class="pre">pdb</span></code>.</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">...</span>
<span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">79</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">pdb</span></code> notes where it has stopped execution and, what line is about to be executed (in our case, <code class="docutils literal notranslate"><span class="pre">obj</span> <span class="pre">=</span> <span class="pre">self.search(self.args)</span></code>), and ask what you would like to do.</p>
<section id="listing-surrounding-lines-of-code">
<h3>Listing surrounding lines of code<a class="headerlink" href="#listing-surrounding-lines-of-code" title="Permalink to this headline"></a></h3>
<p>When you have the <code class="docutils literal notranslate"><span class="pre">pdb</span></code> prompt <code class="docutils literal notranslate"><span class="pre">(Pdb)</span></code>, you can type in different commands to explore the code. The
first one you should know is <code class="docutils literal notranslate"><span class="pre">list</span></code> (you can type <code class="docutils literal notranslate"><span class="pre">l</span></code> for short):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">l</span>
<span class="mi">43</span>
<span class="mi">44</span> <span class="n">key</span> <span class="o">=</span> <span class="s2">&quot;test&quot;</span>
<span class="mi">45</span>
<span class="mi">46</span> <span class="k">def</span> <span class="nf">func</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="mi">47</span> <span class="kn">from</span> <span class="nn">evennia</span> <span class="kn">import</span> <span class="n">set_trace</span><span class="p">;</span> <span class="n">set_trace</span><span class="p">()</span> <span class="c1"># &lt;--- start of debugger</span>
<span class="mi">48</span> <span class="o">-&gt;</span> <span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="mi">49</span> <span class="bp">self</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You&#39;ve found </span><span class="si">{}</span><span class="s2">.&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">obj</span><span class="o">.</span><span class="n">get_display_name</span><span class="p">()))</span>
<span class="mi">50</span>
<span class="mi">51</span> <span class="c1"># -------------------------------------------------------------</span>
<span class="mi">52</span> <span class="c1">#</span>
<span class="mi">53</span> <span class="c1"># The default commands inherit from</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>Okay, this didn’t do anything spectacular, but when you become more confident with <code class="docutils literal notranslate"><span class="pre">pdb</span></code> and find
yourself in lots of different files, you sometimes need to see what’s around in code. Notice that
there is a little arrow (<code class="docutils literal notranslate"><span class="pre">-&gt;</span></code>) before the line that is about to be executed.</p>
<p>This is important: <strong>about to be</strong>, not <strong>has just been</strong>. You need to tell <code class="docutils literal notranslate"><span class="pre">pdb</span></code> to go on (we’ll
soon see how).</p>
</section>
<section id="examining-variables">
<h3>Examining variables<a class="headerlink" href="#examining-variables" title="Permalink to this headline"></a></h3>
<p><code class="docutils literal notranslate"><span class="pre">pdb</span></code> allows you to examine variables (or really, to run any Python instruction). It is very useful
to know the values of variables at a specific line. To see a variable, just type its name (as if
you were in the Python interpreter:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="bp">self</span>
<span class="o">&lt;</span><span class="n">commands</span><span class="o">.</span><span class="n">command</span><span class="o">.</span><span class="n">CmdTest</span> <span class="nb">object</span> <span class="n">at</span> <span class="mh">0x045A0990</span><span class="o">&gt;</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="bp">self</span><span class="o">.</span><span class="n">args</span>
<span class="sa">u</span><span class="s1">&#39;&#39;</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="bp">self</span><span class="o">.</span><span class="n">caller</span>
<span class="o">&lt;</span><span class="n">Character</span><span class="p">:</span> <span class="n">XXX</span><span class="o">&gt;</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>If you try to see the variable <code class="docutils literal notranslate"><span class="pre">obj</span></code>, you’ll get an error:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">obj</span>
<span class="o">***</span> <span class="ne">NameError</span><span class="p">:</span> <span class="n">name</span> <span class="s1">&#39;obj&#39;</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">defined</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>That figures, since at this point, we haven’t created the variable yet.</p>
<blockquote>
<div><p>Examining variable in this way is quite powerful. You can even run Python code and keep on
executing, which can help to check that your fix is actually working when you have identified an
error. If you have variable names that will conflict with <code class="docutils literal notranslate"><span class="pre">pdb</span></code> commands (like a <code class="docutils literal notranslate"><span class="pre">list</span></code>
variable), you can prefix your variable with <code class="docutils literal notranslate"><span class="pre">!</span></code>, to tell <code class="docutils literal notranslate"><span class="pre">pdb</span></code> that what follows is Python code.</p>
</div></blockquote>
</section>
<section id="executing-the-current-line">
<h3>Executing the current line<a class="headerlink" href="#executing-the-current-line" title="Permalink to this headline"></a></h3>
<p>It’s time we asked <code class="docutils literal notranslate"><span class="pre">pdb</span></code> to execute the current line. To do so, use the <code class="docutils literal notranslate"><span class="pre">next</span></code> command. You can
shorten it by just typing <code class="docutils literal notranslate"><span class="pre">n</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">n</span>
<span class="ne">AttributeError</span><span class="p">:</span> <span class="s2">&quot;&#39;CmdTest&#39; object has no attribute &#39;search&#39;&quot;</span>
<span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">79</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">Pdb</span></code> is complaining that you try to call the <code class="docutils literal notranslate"><span class="pre">search</span></code> method on a command… whereas there’s no
<code class="docutils literal notranslate"><span class="pre">search</span></code> method on commands. The character executing the command is in <code class="docutils literal notranslate"><span class="pre">self.caller</span></code>, so we might
change our line:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
</pre></div>
</div>
</section>
<section id="letting-the-program-run">
<h3>Letting the program run<a class="headerlink" href="#letting-the-program-run" title="Permalink to this headline"></a></h3>
<p><code class="docutils literal notranslate"><span class="pre">pdb</span></code> is waiting to execute the same instruction… it provoked an error but it’s ready to try
again, just in case. We have fixed it in theory, but we need to reload, so we need to enter a
command. To tell <code class="docutils literal notranslate"><span class="pre">pdb</span></code> to terminate and keep on running the program, use the <code class="docutils literal notranslate"><span class="pre">continue</span></code> (or <code class="docutils literal notranslate"><span class="pre">c</span></code>)
command:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">c</span>
<span class="o">...</span>
</pre></div>
</div>
<p>You see an error being caught, that’s the error we have fixed… or hope to have. Let’s reload the
game and try again. You need to run <code class="docutils literal notranslate"><span class="pre">evennia</span> <span class="pre">istart</span></code> again and then run <code class="docutils literal notranslate"><span class="pre">test</span></code> to get into the
command again.</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">79</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">pdb</span></code> is about to run the line again.</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">n</span>
<span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">80</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="bp">self</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You&#39;ve found </span><span class="si">{}</span><span class="s2">.&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">obj</span><span class="o">.</span><span class="n">get_display_name</span><span class="p">()))</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>This time the line ran without error. Let’s see what is in the <code class="docutils literal notranslate"><span class="pre">obj</span></code> variable:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">obj</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="nb">print</span> <span class="n">obj</span>
<span class="kc">None</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>We have entered the <code class="docutils literal notranslate"><span class="pre">test</span></code> command without parameter, so no object could be found in the search
(<code class="docutils literal notranslate"><span class="pre">self.args</span></code> is an empty string).</p>
<p>Let’s allow the command to continue and try to use an object name as parameter (although, we should
fix that bug too, it would be better):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">c</span>
<span class="o">...</span>
</pre></div>
</div>
<p>Notice that you’ll have an error in the game this time. Let’s try with a valid parameter. I have
another character, <code class="docutils literal notranslate"><span class="pre">barkeep</span></code>, in this room:</p>
<p><code class="docutils literal notranslate"><span class="pre">test</span> <span class="pre">barkeep</span></code></p>
<p>And again, the command freezes, and we have the debugger opened in the console.</p>
<p>Let’s execute this line right away:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">79</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="n">obj</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">caller</span><span class="o">.</span><span class="n">search</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">args</span><span class="p">)</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">n</span>
<span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">80</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="bp">self</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You&#39;ve found </span><span class="si">{}</span><span class="s2">.&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">obj</span><span class="o">.</span><span class="n">get_display_name</span><span class="p">()))</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">obj</span>
<span class="o">&lt;</span><span class="n">Character</span><span class="p">:</span> <span class="n">barkeep</span><span class="o">&gt;</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>At least this time we have found the object. Let’s process…</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">Pdb</span><span class="p">)</span> <span class="n">n</span>
<span class="ne">TypeError</span><span class="p">:</span> <span class="s1">&#39;get_display_name() takes exactly 2 arguments (1 given)&#39;</span>
<span class="o">&gt;</span> <span class="o">.../</span><span class="n">mygame</span><span class="o">/</span><span class="n">commands</span><span class="o">/</span><span class="n">command</span><span class="o">.</span><span class="n">py</span><span class="p">(</span><span class="mi">80</span><span class="p">)</span><span class="n">func</span><span class="p">()</span>
<span class="o">-&gt;</span> <span class="bp">self</span><span class="o">.</span><span class="n">msg</span><span class="p">(</span><span class="s2">&quot;You&#39;ve found </span><span class="si">{}</span><span class="s2">.&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">obj</span><span class="o">.</span><span class="n">get_display_name</span><span class="p">()))</span>
<span class="p">(</span><span class="n">Pdb</span><span class="p">)</span>
</pre></div>
</div>
<p>As an exercise, fix this error, reload and run the debugger again. Nothing better than some
experimenting!</p>
<p>Your debugging will often follow the same strategy:</p>
<ol class="simple">
<li><p>Receive an error you don’t understand.</p></li>
<li><p>Put a breaking point <strong>BEFORE</strong> the error occurs.</p></li>
<li><p>Run the code again and see the debugger open.</p></li>
<li><p>Run the program line by line,examining variables, checking the logic of instructions.</p></li>
<li><p>Continue and try again, each step a bit further toward the truth and the working feature.</p></li>
</ol>
</section>
<section id="stepping-through-a-function">
<h3>Stepping through a function<a class="headerlink" href="#stepping-through-a-function" title="Permalink to this headline"></a></h3>
<p><code class="docutils literal notranslate"><span class="pre">n</span></code> is useful, but it will avoid stepping inside of functions if it can. But most of the time, when
we have an error we don’t understand, it’s because we use functions or methods in a way that wasn’t
intended by the developer of the API. Perhaps using wrong arguments, or calling the function in a
situation that would cause a bug. When we have a line in the debugger that calls a function or
method, we can “step” to examine it further. For instance, in the previous example, when <code class="docutils literal notranslate"><span class="pre">pdb</span></code> was
about to execute <code class="docutils literal notranslate"><span class="pre">obj</span> <span class="pre">=</span> <span class="pre">self.caller.search(self.args)</span></code>, we may want to see what happens inside of
the <code class="docutils literal notranslate"><span class="pre">search</span></code> method.</p>
<p>To do so, use the <code class="docutils literal notranslate"><span class="pre">step</span></code> (or <code class="docutils literal notranslate"><span class="pre">s</span></code>) command. This command will show you the definition of the
function/method and you can then use <code class="docutils literal notranslate"><span class="pre">n</span></code> as before to see it line-by-line. In our little example,
stepping through a function or method isn’t that useful, but when you have an impressive set of
commands, functions and so on, it might really be handy to examine some feature and make sure they
operate as planned.</p>
</section>
</section>
<section id="cheat-sheet-of-pdb-pudb-commands">
<h2>Cheat-sheet of pdb/pudb commands<a class="headerlink" href="#cheat-sheet-of-pdb-pudb-commands" title="Permalink to this headline"></a></h2>
<p>PuDB and Pdb share the same commands. The only real difference is how it’s presented. The <code class="docutils literal notranslate"><span class="pre">look</span></code>
command is not needed much in <code class="docutils literal notranslate"><span class="pre">pudb</span></code> since it displays the code directly in its user interface.</p>
<table class="colwidths-auto docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Pdb/PuDB command</p></th>
<th class="head"><p>To do what</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>list (or l)</p></td>
<td><p>List the lines around the point of execution (not needed for <code class="docutils literal notranslate"><span class="pre">pudb</span></code>, it will show</p></td>
</tr>
<tr class="row-odd"><td><p>this directly).</p></td>
<td><p></p></td>
</tr>
<tr class="row-even"><td><p>print (or p)</p></td>
<td><p>Display one or several variables.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">!</span></code></p></td>
<td><p>Run Python code (using a <code class="docutils literal notranslate"><span class="pre">!</span></code> is often optional).</p></td>
</tr>
<tr class="row-even"><td><p>continue (or c)</p></td>
<td><p>Continue execution and terminate the debugger for this time.</p></td>
</tr>
<tr class="row-odd"><td><p>next (or n)</p></td>
<td><p>Execute the current line and goes to the next one.</p></td>
</tr>
<tr class="row-even"><td><p>step (or s)</p></td>
<td><p>Step inside of a function or method to examine it.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">&lt;RETURN&gt;</span></code></p></td>
<td><p>Repeat the last command (don’t type <code class="docutils literal notranslate"><span class="pre">n</span></code> repeatedly, just type it once and then press</p></td>
</tr>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">&lt;RETURN&gt;</span></code> to repeat it).</p></td>
<td><p></p></td>
</tr>
</tbody>
</table>
<p>If you want to learn more about debugging with Pdb, you will find an <a class="reference external" href="https://pymotw.com/3/pdb/">interesting tutorial on that
topic here</a>.</p>
</section>
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<p><h3><a href="index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Debugging</a><ul>
<li><a class="reference internal" href="#debugging-evennia">Debugging Evennia</a></li>
<li><a class="reference internal" href="#a-simple-example-using-pdb">A simple example using pdb</a><ul>
<li><a class="reference internal" href="#listing-surrounding-lines-of-code">Listing surrounding lines of code</a></li>
<li><a class="reference internal" href="#examining-variables">Examining variables</a></li>
<li><a class="reference internal" href="#executing-the-current-line">Executing the current line</a></li>
<li><a class="reference internal" href="#letting-the-program-run">Letting the program run</a></li>
<li><a class="reference internal" href="#stepping-through-a-function">Stepping through a function</a></li>
</ul>
</li>
<li><a class="reference internal" href="#cheat-sheet-of-pdb-pudb-commands">Cheat-sheet of pdb/pudb commands</a></li>
</ul>
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