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               180 181    <div class="inline-search" role="search">182        <form class="inline-search" action="../search.html" method="get">183          <input placeholder="Quick search" aria-label="Quick search" type="search" name="q" id="search-box">184          <input type="submit" value="Go">185        </form>186    </div>187                     |188                </li>189            <li class="right">190<label class="theme-selector-label">191    Theme192    <select class="theme-selector" oninput="activateTheme(this.value)">193        <option value="auto" selected>Auto</option>194        <option value="light">Light</option>195        <option value="dark">Dark</option>196    </select>197</label> |</li>198            199      </ul>200    </div>    201 202    <div class="document">203      <div class="documentwrapper">204        <div class="bodywrapper">205          <div class="body" role="main">206            207  <section id="module-linecache">208<span id="linecache-random-access-to-text-lines"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">linecache</span></code> — Random access to text lines<a class="headerlink" href="#module-linecache" title="Link to this heading">¶</a></h1>209<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/main/Lib/linecache.py">Lib/linecache.py</a></p>210<hr class="docutils" />211<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">linecache</span></code> module allows one to get any line from a Python source file, while212attempting to optimize internally, using a cache, the common case where many213lines are read from a single file.  This is used by the <a class="reference internal" href="traceback.html#module-traceback" title="traceback: Print or retrieve a stack traceback."><code class="xref py py-mod docutils literal notranslate"><span class="pre">traceback</span></code></a> module214to retrieve source lines for inclusion in  the formatted traceback.</p>215<p>The <a class="reference internal" href="tokenize.html#tokenize.open" title="tokenize.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">tokenize.open()</span></code></a> function is used to open files. This216function uses <a class="reference internal" href="tokenize.html#tokenize.detect_encoding" title="tokenize.detect_encoding"><code class="xref py py-func docutils literal notranslate"><span class="pre">tokenize.detect_encoding()</span></code></a> to get the encoding of the217file; in the absence of an encoding token, the file encoding defaults to UTF-8.</p>218<p>The <code class="xref py py-mod docutils literal notranslate"><span class="pre">linecache</span></code> module defines the following functions:</p>219<dl class="py function">220<dt class="sig sig-object py" id="linecache.getline">221<span class="sig-prename descclassname"><span class="pre">linecache.</span></span><span class="sig-name descname"><span class="pre">getline</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">lineno</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">module_globals</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#linecache.getline" title="Link to this definition">¶</a></dt>222<dd><p>Get line <em>lineno</em> from file named <em>filename</em>. This function will never raise an223exception — it will return <code class="docutils literal notranslate"><span class="pre">''</span></code> on errors (the terminating newline character224will be included for lines that are found).</p>225<p id="index-0">If <em>filename</em> indicates a frozen module (starting with <code class="docutils literal notranslate"><span class="pre">'&lt;frozen</span> <span class="pre">'</span></code>), the function226will attempt to get the real file name from <code class="docutils literal notranslate"><span class="pre">module_globals['__file__']</span></code> if227<em>module_globals</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>228<p>If a file named <em>filename</em> is not found, the function first checks229for a <span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0302/"><strong>PEP 302</strong></a> <code class="docutils literal notranslate"><span class="pre">__loader__</span></code> in <em>module_globals</em>.230If there is such a loader and it defines a <code class="docutils literal notranslate"><span class="pre">get_source</span></code> method,231then that determines the source lines232(if <code class="docutils literal notranslate"><span class="pre">get_source()</span></code> returns <code class="docutils literal notranslate"><span class="pre">None</span></code>, then <code class="docutils literal notranslate"><span class="pre">''</span></code> is returned).233Finally, if <em>filename</em> is a relative filename,234it is looked up relative to the entries in the module search path, <code class="docutils literal notranslate"><span class="pre">sys.path</span></code>.</p>235<div class="versionchanged">236<p><span class="versionmodified changed">Changed in version 3.14: </span>Support <em>filename</em> of frozen modules.</p>237</div>238</dd></dl>239 240<dl class="py function">241<dt class="sig sig-object py" id="linecache.clearcache">242<span class="sig-prename descclassname"><span class="pre">linecache.</span></span><span class="sig-name descname"><span class="pre">clearcache</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#linecache.clearcache" title="Link to this definition">¶</a></dt>243<dd><p>Clear the cache.  Use this function if you no longer need lines from files244previously read using <a class="reference internal" href="#linecache.getline" title="linecache.getline"><code class="xref py py-func docutils literal notranslate"><span class="pre">getline()</span></code></a>.</p>245</dd></dl>246 247<dl class="py function">248<dt class="sig sig-object py" id="linecache.checkcache">249<span class="sig-prename descclassname"><span class="pre">linecache.</span></span><span class="sig-name descname"><span class="pre">checkcache</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#linecache.checkcache" title="Link to this definition">¶</a></dt>250<dd><p>Check the cache for validity.  Use this function if files in the cache  may have251changed on disk, and you require the updated version.  If <em>filename</em> is omitted,252it will check all the entries in the cache.</p>253</dd></dl>254 255<dl class="py function">256<dt class="sig sig-object py" id="linecache.lazycache">257<span class="sig-prename descclassname"><span class="pre">linecache.</span></span><span class="sig-name descname"><span class="pre">lazycache</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">filename</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">module_globals</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#linecache.lazycache" title="Link to this definition">¶</a></dt>258<dd><p>Capture enough detail about a non-file-based module to permit getting its259lines later via <a class="reference internal" href="#linecache.getline" title="linecache.getline"><code class="xref py py-func docutils literal notranslate"><span class="pre">getline()</span></code></a> even if <em>module_globals</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code> in the later260call. This avoids doing I/O until a line is actually needed, without having261to carry the module globals around indefinitely.</p>262<div class="versionadded">263<p><span class="versionmodified added">Added in version 3.5.</span></p>264</div>265</dd></dl>266 267<p>Example:</p>268<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span><span class="w"> </span><span class="nn">linecache</span>269<span class="gp">&gt;&gt;&gt; </span><span class="n">linecache</span><span class="o">.</span><span class="n">getline</span><span class="p">(</span><span class="n">linecache</span><span class="o">.</span><span class="vm">__file__</span><span class="p">,</span> <span class="mi">8</span><span class="p">)</span>270<span class="go">&#39;import sys\n&#39;</span>271</pre></div>272</div>273</section>274 275 276            <div class="clearer"></div>277          </div>278        </div>279      </div>280      <div class="sphinxsidebar" role="navigation" aria-label="Main">281        <div class="sphinxsidebarwrapper">282  <div>283    <h4>Previous topic</h4>284    <p class="topless"><a href="fnmatch.html"285                          title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">fnmatch</span></code> — Unix filename pattern matching</a></p>286  </div>287  <div>288    <h4>Next topic</h4>289    <p class="topless"><a href="shutil.html"290                          title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">shutil</span></code> — High-level file operations</a></p>291  </div>292  <script>293    document.addEventListener('DOMContentLoaded', () => {294        const title = document.querySelector('meta[property="og:title"]').content;295        const elements = document.querySelectorAll('.improvepage');296        const pageurl = window.location.href.split('?')[0];297        elements.forEach(element => {298            const url = new URL(element.href.split('?')[0].replace("-nojs", ""));299            url.searchParams.set('pagetitle', title);300            url.searchParams.set('pageurl', pageurl);301            url.searchParams.set('pagesource', "library/linecache.rst");302            element.href = url.toString();303        });304    });305  </script>306  <div role="note" aria-label="source link">307    <h3>This page</h3>308    <ul class="this-page-menu">309      <li><a href="../bugs.html">Report a bug</a></li>310      <li><a class="improvepage" href="../improve-page-nojs.html">Improve this page</a></li>311      <li>312        <a href="https://github.com/python/cpython/blob/main/Doc/library/linecache.rst?plain=1"313            rel="nofollow">Show source314        </a>315      </li>316      317    </ul>318  </div>319        </div>320<div id="sidebarbutton" title="Collapse sidebar">321<span>«</span>322</div>323 324      </div>325      <div class="clearer"></div>326    </div>  327    <div class="related" role="navigation" aria-label="Related">328      <h3>Navigation</h3>329      <ul>330        <li class="right" style="margin-right: 10px">331          <a href="../genindex.html" title="General Index"332             >index</a></li>333        <li class="right" >334          <a href="../py-modindex.html" title="Python Module Index"335             >modules</a> |</li>336        <li class="right" >337          <a href="shutil.html" title="shutil — High-level file operations"338             >next</a> |</li>339        <li class="right" >340          <a href="fnmatch.html" title="fnmatch — Unix filename pattern matching"341             >previous</a> |</li>342 343          <li><img src="../_static/py.svg" alt="Python logo" style="vertical-align: middle; 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