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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>28.10. traceback — Print or retrieve a stack traceback — Python 2.7.16 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.16 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="28.11. __future__ — Future statement definitions" href="__future__.html" /> <link rel="prev" title="28.9. atexit — Exit handlers" href="atexit.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/2/library/traceback.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="__future__.html" title="28.11. __future__ — Future statement definitions" accesskey="N">next</a> |</li> <li class="right" > <a href="atexit.html" title="28.9. atexit — Exit handlers" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.16 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> »</li> <li class="nav-item nav-item-2"><a href="python.html" accesskey="U">28. Python Runtime Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-traceback"> <span id="traceback-print-or-retrieve-a-stack-traceback"></span><h1>28.10. <a class="reference internal" href="#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> — Print or retrieve a stack traceback<a class="headerlink" href="#module-traceback" title="Permalink to this headline">¶</a></h1> <p>This module provides a standard interface to extract, format and print stack traces of Python programs. It exactly mimics the behavior of the Python interpreter when it prints a stack trace. This is useful when you want to print stack traces under program control, such as in a “wrapper” around the interpreter.</p> <p id="index-0">The module uses traceback objects — this is the object type that is stored in the variables <a class="reference internal" href="sys.html#sys.exc_traceback" title="sys.exc_traceback"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.exc_traceback</span></code></a> (deprecated) and <a class="reference internal" href="sys.html#sys.last_traceback" title="sys.last_traceback"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.last_traceback</span></code></a> and returned as the third item from <a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.exc_info()</span></code></a>.</p> <p>The module defines the following functions:</p> <dl class="function"> <dt id="traceback.print_tb"> <code class="descclassname">traceback.</code><code class="descname">print_tb</code><span class="sig-paren">(</span><em>tb</em><span class="optional">[</span>, <em>limit</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.print_tb" title="Permalink to this definition">¶</a></dt> <dd><p>Print up to <em>limit</em> stack trace entries from the traceback object <em>tb</em>. If <em>limit</em> is omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, all entries are printed. If <em>file</em> is omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the output goes to <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>; otherwise it should be an open file or file-like object to receive the output.</p> </dd></dl> <dl class="function"> <dt id="traceback.print_exception"> <code class="descclassname">traceback.</code><code class="descname">print_exception</code><span class="sig-paren">(</span><em>etype</em>, <em>value</em>, <em>tb</em><span class="optional">[</span>, <em>limit</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.print_exception" title="Permalink to this definition">¶</a></dt> <dd><p>Print exception information and up to <em>limit</em> stack trace entries from the traceback <em>tb</em> to <em>file</em>. This differs from <a class="reference internal" href="#traceback.print_tb" title="traceback.print_tb"><code class="xref py py-func docutils literal notranslate"><span class="pre">print_tb()</span></code></a> in the following ways: (1) if <em>tb</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, it prints a header <code class="docutils literal notranslate"><span class="pre">Traceback</span> <span class="pre">(most</span> <span class="pre">recent</span> <span class="pre">call</span> <span class="pre">last):</span></code>; (2) it prints the exception <em>etype</em> and <em>value</em> after the stack trace; (3) if <em>etype</em> is <a class="reference internal" href="exceptions.html#exceptions.SyntaxError" title="exceptions.SyntaxError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SyntaxError</span></code></a> and <em>value</em> has the appropriate format, it prints the line where the syntax error occurred with a caret indicating the approximate position of the error.</p> </dd></dl> <dl class="function"> <dt id="traceback.print_exc"> <code class="descclassname">traceback.</code><code class="descname">print_exc</code><span class="sig-paren">(</span><span class="optional">[</span><em>limit</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.print_exc" title="Permalink to this definition">¶</a></dt> <dd><p>This is a shorthand for <code class="docutils literal notranslate"><span class="pre">print_exception(sys.exc_type,</span> <span class="pre">sys.exc_value,</span> <span class="pre">sys.exc_traceback,</span> <span class="pre">limit,</span> <span class="pre">file)</span></code>. (In fact, it uses <a class="reference internal" href="sys.html#sys.exc_info" title="sys.exc_info"><code class="xref py py-func docutils literal notranslate"><span class="pre">sys.exc_info()</span></code></a> to retrieve the same information in a thread-safe way instead of using the deprecated variables.)</p> </dd></dl> <dl class="function"> <dt id="traceback.format_exc"> <code class="descclassname">traceback.</code><code class="descname">format_exc</code><span class="sig-paren">(</span><span class="optional">[</span><em>limit</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_exc" title="Permalink to this definition">¶</a></dt> <dd><p>This is like <code class="docutils literal notranslate"><span class="pre">print_exc(limit)</span></code> but returns a string instead of printing to a file.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 2.4.</span></p> </div> </dd></dl> <dl class="function"> <dt id="traceback.print_last"> <code class="descclassname">traceback.</code><code class="descname">print_last</code><span class="sig-paren">(</span><span class="optional">[</span><em>limit</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.print_last" title="Permalink to this definition">¶</a></dt> <dd><p>This is a shorthand for <code class="docutils literal notranslate"><span class="pre">print_exception(sys.last_type,</span> <span class="pre">sys.last_value,</span> <span class="pre">sys.last_traceback,</span> <span class="pre">limit,</span> <span class="pre">file)</span></code>. In general it will work only after an exception has reached an interactive prompt (see <a class="reference internal" href="sys.html#sys.last_type" title="sys.last_type"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.last_type</span></code></a>).</p> </dd></dl> <dl class="function"> <dt id="traceback.print_stack"> <code class="descclassname">traceback.</code><code class="descname">print_stack</code><span class="sig-paren">(</span><span class="optional">[</span><em>f</em><span class="optional">[</span>, <em>limit</em><span class="optional">[</span>, <em>file</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.print_stack" title="Permalink to this definition">¶</a></dt> <dd><p>This function prints a stack trace from its invocation point. The optional <em>f</em> argument can be used to specify an alternate stack frame to start. The optional <em>limit</em> and <em>file</em> arguments have the same meaning as for <a class="reference internal" href="#traceback.print_exception" title="traceback.print_exception"><code class="xref py py-func docutils literal notranslate"><span class="pre">print_exception()</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="traceback.extract_tb"> <code class="descclassname">traceback.</code><code class="descname">extract_tb</code><span class="sig-paren">(</span><em>tb</em><span class="optional">[</span>, <em>limit</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.extract_tb" title="Permalink to this definition">¶</a></dt> <dd><p>Return a list of up to <em>limit</em> “pre-processed” stack trace entries extracted from the traceback object <em>tb</em>. It is useful for alternate formatting of stack traces. If <em>limit</em> is omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, all entries are extracted. A “pre-processed” stack trace entry is a 4-tuple (<em>filename</em>, <em>line number</em>, function name*, <em>text</em>) representing the information that is usually printed for a stack trace. The <em>text</em> is a string with leading and trailing whitespace stripped; if the source is not available it is <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="function"> <dt id="traceback.extract_stack"> <code class="descclassname">traceback.</code><code class="descname">extract_stack</code><span class="sig-paren">(</span><span class="optional">[</span><em>f</em><span class="optional">[</span>, <em>limit</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.extract_stack" title="Permalink to this definition">¶</a></dt> <dd><p>Extract the raw traceback from the current stack frame. The return value has the same format as for <a class="reference internal" href="#traceback.extract_tb" title="traceback.extract_tb"><code class="xref py py-func docutils literal notranslate"><span class="pre">extract_tb()</span></code></a>. The optional <em>f</em> and <em>limit</em> arguments have the same meaning as for <a class="reference internal" href="#traceback.print_stack" title="traceback.print_stack"><code class="xref py py-func docutils literal notranslate"><span class="pre">print_stack()</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="traceback.format_list"> <code class="descclassname">traceback.</code><code class="descname">format_list</code><span class="sig-paren">(</span><em>extracted_list</em><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_list" title="Permalink to this definition">¶</a></dt> <dd><p>Given a list of tuples as returned by <a class="reference internal" href="#traceback.extract_tb" title="traceback.extract_tb"><code class="xref py py-func docutils literal notranslate"><span class="pre">extract_tb()</span></code></a> or <a class="reference internal" href="#traceback.extract_stack" title="traceback.extract_stack"><code class="xref py py-func docutils literal notranslate"><span class="pre">extract_stack()</span></code></a>, return a list of strings ready for printing. Each string in the resulting list corresponds to the item with the same index in the argument list. Each string ends in a newline; the strings may contain internal newlines as well, for those items whose source text line is not <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="function"> <dt id="traceback.format_exception_only"> <code class="descclassname">traceback.</code><code class="descname">format_exception_only</code><span class="sig-paren">(</span><em>etype</em>, <em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_exception_only" title="Permalink to this definition">¶</a></dt> <dd><p>Format the exception part of a traceback. The arguments are the exception type, <em>etype</em> and <em>value</em> such as given by <code class="docutils literal notranslate"><span class="pre">sys.last_type</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.last_value</span></code>. The return value is a list of strings, each ending in a newline. Normally, the list contains a single string; however, for <a class="reference internal" href="exceptions.html#exceptions.SyntaxError" title="exceptions.SyntaxError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">SyntaxError</span></code></a> exceptions, it contains several lines that (when printed) display detailed information about where the syntax error occurred. The message indicating which exception occurred is the always last string in the list.</p> </dd></dl> <dl class="function"> <dt id="traceback.format_exception"> <code class="descclassname">traceback.</code><code class="descname">format_exception</code><span class="sig-paren">(</span><em>etype</em>, <em>value</em>, <em>tb</em><span class="optional">[</span>, <em>limit</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_exception" title="Permalink to this definition">¶</a></dt> <dd><p>Format a stack trace and the exception information. The arguments have the same meaning as the corresponding arguments to <a class="reference internal" href="#traceback.print_exception" title="traceback.print_exception"><code class="xref py py-func docutils literal notranslate"><span class="pre">print_exception()</span></code></a>. The return value is a list of strings, each ending in a newline and some containing internal newlines. When these lines are concatenated and printed, exactly the same text is printed as does <a class="reference internal" href="#traceback.print_exception" title="traceback.print_exception"><code class="xref py py-func docutils literal notranslate"><span class="pre">print_exception()</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="traceback.format_tb"> <code class="descclassname">traceback.</code><code class="descname">format_tb</code><span class="sig-paren">(</span><em>tb</em><span class="optional">[</span>, <em>limit</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_tb" title="Permalink to this definition">¶</a></dt> <dd><p>A shorthand for <code class="docutils literal notranslate"><span class="pre">format_list(extract_tb(tb,</span> <span class="pre">limit))</span></code>.</p> </dd></dl> <dl class="function"> <dt id="traceback.format_stack"> <code class="descclassname">traceback.</code><code class="descname">format_stack</code><span class="sig-paren">(</span><span class="optional">[</span><em>f</em><span class="optional">[</span>, <em>limit</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#traceback.format_stack" title="Permalink to this definition">¶</a></dt> <dd><p>A shorthand for <code class="docutils literal notranslate"><span class="pre">format_list(extract_stack(f,</span> <span class="pre">limit))</span></code>.</p> </dd></dl> <dl class="function"> <dt id="traceback.tb_lineno"> <code class="descclassname">traceback.</code><code class="descname">tb_lineno</code><span class="sig-paren">(</span><em>tb</em><span class="sig-paren">)</span><a class="headerlink" href="#traceback.tb_lineno" title="Permalink to this definition">¶</a></dt> <dd><p>This function returns the current line number set in the traceback object. This function was necessary because in versions of Python prior to 2.3 when the <a class="reference internal" href="../using/cmdline.html#cmdoption-o"><code class="xref std std-option docutils literal notranslate"><span class="pre">-O</span></code></a> flag was passed to Python the <code class="docutils literal notranslate"><span class="pre">tb.tb_lineno</span></code> was not updated correctly. This function has no use in versions past 2.3.</p> </dd></dl> <div class="section" id="traceback-examples"> <span id="traceback-example"></span><h2>28.10.1. Traceback Examples<a class="headerlink" href="#traceback-examples" title="Permalink to this headline">¶</a></h2> <p>This simple example implements a basic read-eval-print loop, similar to (but less useful than) the standard Python interactive interpreter loop. For a more complete implementation of the interpreter loop, refer to the <a class="reference internal" href="code.html#module-code" title="code: Facilities to implement read-eval-print loops."><code class="xref py py-mod docutils literal notranslate"><span class="pre">code</span></code></a> module.</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">traceback</span> <span class="k">def</span> <span class="nf">run_user_code</span><span class="p">(</span><span class="n">envdir</span><span class="p">):</span> <span class="n">source</span> <span class="o">=</span> <span class="n">raw_input</span><span class="p">(</span><span class="s2">">>> "</span><span class="p">)</span> <span class="k">try</span><span class="p">:</span> <span class="n">exec</span> <span class="n">source</span> <span class="ow">in</span> <span class="n">envdir</span> <span class="k">except</span><span class="p">:</span> <span class="nb">print</span> <span class="s2">"Exception in user code:"</span> <span class="nb">print</span> <span class="s1">'-'</span><span class="o">*</span><span class="mi">60</span> <span class="n">traceback</span><span class="o">.</span><span class="n">print_exc</span><span class="p">(</span><span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span> <span class="nb">print</span> <span class="s1">'-'</span><span class="o">*</span><span class="mi">60</span> <span class="n">envdir</span> <span class="o">=</span> <span class="p">{}</span> <span class="k">while</span> <span class="mi">1</span><span class="p">:</span> <span class="n">run_user_code</span><span class="p">(</span><span class="n">envdir</span><span class="p">)</span> </pre></div> </div> <p>The following example demonstrates the different ways to print and format the exception and traceback:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">traceback</span> <span class="k">def</span> <span class="nf">lumberjack</span><span class="p">():</span> <span class="n">bright_side_of_death</span><span class="p">()</span> <span class="k">def</span> <span class="nf">bright_side_of_death</span><span class="p">():</span> <span class="k">return</span> <span class="nb">tuple</span><span class="p">()[</span><span class="mi">0</span><span class="p">]</span> <span class="k">try</span><span class="p">:</span> <span class="n">lumberjack</span><span class="p">()</span> <span class="k">except</span> <span class="ne">IndexError</span><span class="p">:</span> <span class="n">exc_type</span><span class="p">,</span> <span class="n">exc_value</span><span class="p">,</span> <span class="n">exc_traceback</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">exc_info</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"*** print_tb:"</span> <span class="n">traceback</span><span class="o">.</span><span class="n">print_tb</span><span class="p">(</span><span class="n">exc_traceback</span><span class="p">,</span> <span class="n">limit</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span> <span class="nb">print</span> <span class="s2">"*** print_exception:"</span> <span class="n">traceback</span><span class="o">.</span><span class="n">print_exception</span><span class="p">(</span><span class="n">exc_type</span><span class="p">,</span> <span class="n">exc_value</span><span class="p">,</span> <span class="n">exc_traceback</span><span class="p">,</span> <span class="n">limit</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">file</span><span class="o">=</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="p">)</span> <span class="nb">print</span> <span class="s2">"*** print_exc:"</span> <span class="n">traceback</span><span class="o">.</span><span class="n">print_exc</span><span class="p">()</span> <span class="nb">print</span> <span class="s2">"*** format_exc, first and last line:"</span> <span class="n">formatted_lines</span> <span class="o">=</span> <span class="n">traceback</span><span class="o">.</span><span class="n">format_exc</span><span class="p">()</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="nb">print</span> <span class="n">formatted_lines</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="nb">print</span> <span class="n">formatted_lines</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="nb">print</span> <span class="s2">"*** format_exception:"</span> <span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">traceback</span><span class="o">.</span><span class="n">format_exception</span><span class="p">(</span><span class="n">exc_type</span><span class="p">,</span> <span class="n">exc_value</span><span class="p">,</span> <span class="n">exc_traceback</span><span class="p">))</span> <span class="nb">print</span> <span class="s2">"*** extract_tb:"</span> <span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">traceback</span><span class="o">.</span><span class="n">extract_tb</span><span class="p">(</span><span class="n">exc_traceback</span><span class="p">))</span> <span class="nb">print</span> <span class="s2">"*** format_tb:"</span> <span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">traceback</span><span class="o">.</span><span class="n">format_tb</span><span class="p">(</span><span class="n">exc_traceback</span><span class="p">))</span> <span class="nb">print</span> <span class="s2">"*** tb_lineno:"</span><span class="p">,</span> <span class="n">exc_traceback</span><span class="o">.</span><span class="n">tb_lineno</span> </pre></div> </div> <p>The output for the example would look similar to this:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">***</span> <span class="n">print_tb</span><span class="p">:</span> <span class="n">File</span> <span class="s2">"<doctest...>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">10</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span> <span class="n">lumberjack</span><span class="p">()</span> <span class="o">***</span> <span class="n">print_exception</span><span class="p">:</span> <span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span> <span class="n">File</span> <span class="s2">"<doctest...>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">10</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span> <span class="n">lumberjack</span><span class="p">()</span> <span class="n">File</span> <span class="s2">"<doctest...>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">4</span><span class="p">,</span> <span class="ow">in</span> <span class="n">lumberjack</span> <span class="n">bright_side_of_death</span><span class="p">()</span> <span class="ne">IndexError</span><span class="p">:</span> <span class="nb">tuple</span> <span class="n">index</span> <span class="n">out</span> <span class="n">of</span> <span class="nb">range</span> <span class="o">***</span> <span class="n">print_exc</span><span class="p">:</span> <span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span> <span class="n">File</span> <span class="s2">"<doctest...>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">10</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span> <span class="n">lumberjack</span><span class="p">()</span> <span class="n">File</span> <span class="s2">"<doctest...>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">4</span><span class="p">,</span> <span class="ow">in</span> <span class="n">lumberjack</span> <span class="n">bright_side_of_death</span><span class="p">()</span> <span class="ne">IndexError</span><span class="p">:</span> <span class="nb">tuple</span> <span class="n">index</span> <span class="n">out</span> <span class="n">of</span> <span class="nb">range</span> <span class="o">***</span> <span class="n">format_exc</span><span class="p">,</span> <span class="n">first</span> <span class="ow">and</span> <span class="n">last</span> <span class="n">line</span><span class="p">:</span> <span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span> <span class="ne">IndexError</span><span class="p">:</span> <span class="nb">tuple</span> <span class="n">index</span> <span class="n">out</span> <span class="n">of</span> <span class="nb">range</span> <span class="o">***</span> <span class="n">format_exception</span><span class="p">:</span> <span class="p">[</span><span class="s1">'Traceback (most recent call last):</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">' File "<doctest...>", line 10, in <module></span><span class="se">\n</span><span class="s1"> lumberjack()</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">' File "<doctest...>", line 4, in lumberjack</span><span class="se">\n</span><span class="s1"> bright_side_of_death()</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">' File "<doctest...>", line 7, in bright_side_of_death</span><span class="se">\n</span><span class="s1"> return tuple()[0]</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">'IndexError: tuple index out of range</span><span class="se">\n</span><span class="s1">'</span><span class="p">]</span> <span class="o">***</span> <span class="n">extract_tb</span><span class="p">:</span> <span class="p">[(</span><span class="s1">'<doctest...>'</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="s1">'<module>'</span><span class="p">,</span> <span class="s1">'lumberjack()'</span><span class="p">),</span> <span class="p">(</span><span class="s1">'<doctest...>'</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="s1">'lumberjack'</span><span class="p">,</span> <span class="s1">'bright_side_of_death()'</span><span class="p">),</span> <span class="p">(</span><span class="s1">'<doctest...>'</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="s1">'bright_side_of_death'</span><span class="p">,</span> <span class="s1">'return tuple()[0]'</span><span class="p">)]</span> <span class="o">***</span> <span class="n">format_tb</span><span class="p">:</span> <span class="p">[</span><span class="s1">' File "<doctest...>", line 10, in <module></span><span class="se">\n</span><span class="s1"> lumberjack()</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">' File "<doctest...>", line 4, in lumberjack</span><span class="se">\n</span><span class="s1"> bright_side_of_death()</span><span class="se">\n</span><span class="s1">'</span><span class="p">,</span> <span class="s1">' File "<doctest...>", line 7, in bright_side_of_death</span><span class="se">\n</span><span class="s1"> return tuple()[0]</span><span class="se">\n</span><span class="s1">'</span><span class="p">]</span> <span class="o">***</span> <span class="n">tb_lineno</span><span class="p">:</span> <span class="mi">10</span> </pre></div> </div> <p>The following example shows the different ways to print and format the stack:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">traceback</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">another_function</span><span class="p">():</span> <span class="gp">... </span> <span class="n">lumberstack</span><span class="p">()</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">lumberstack</span><span class="p">():</span> <span class="gp">... </span> <span class="n">traceback</span><span class="o">.</span><span class="n">print_stack</span><span class="p">()</span> <span class="gp">... </span> <span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">traceback</span><span class="o">.</span><span class="n">extract_stack</span><span class="p">())</span> <span class="gp">... </span> <span class="nb">print</span> <span class="nb">repr</span><span class="p">(</span><span class="n">traceback</span><span class="o">.</span><span class="n">format_stack</span><span class="p">())</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">another_function</span><span class="p">()</span> <span class="go"> File "<doctest>", line 10, in <module></span> <span class="go"> another_function()</span> <span class="go"> File "<doctest>", line 3, in another_function</span> <span class="go"> lumberstack()</span> <span class="go"> File "<doctest>", line 6, in lumberstack</span> <span class="go"> traceback.print_stack()</span> <span class="go">[('<doctest>', 10, '<module>', 'another_function()'),</span> <span class="go"> ('<doctest>', 3, 'another_function', 'lumberstack()'),</span> <span class="go"> ('<doctest>', 7, 'lumberstack', 'print repr(traceback.extract_stack())')]</span> <span class="go">[' File "<doctest>", line 10, in <module>\n another_function()\n',</span> <span class="go"> ' File "<doctest>", line 3, in another_function\n lumberstack()\n',</span> <span class="go"> ' File "<doctest>", line 8, in lumberstack\n print repr(traceback.format_stack())\n']</span> </pre></div> </div> <p>This last example demonstrates the final few formatting functions:</p> <div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">traceback</span> <span class="gp">>>> </span><span class="n">traceback</span><span class="o">.</span><span class="n">format_list</span><span class="p">([(</span><span class="s1">'spam.py'</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">'<module>'</span><span class="p">,</span> <span class="s1">'spam.eggs()'</span><span class="p">),</span> <span class="gp">... </span> <span class="p">(</span><span class="s1">'eggs.py'</span><span class="p">,</span> <span class="mi">42</span><span class="p">,</span> <span class="s1">'eggs'</span><span class="p">,</span> <span class="s1">'return "bacon"'</span><span class="p">)])</span> <span class="go">[' File "spam.py", line 3, in <module>\n spam.eggs()\n',</span> <span class="go"> ' File "eggs.py", line 42, in eggs\n return "bacon"\n']</span> <span class="gp">>>> </span><span class="n">an_error</span> <span class="o">=</span> <span class="ne">IndexError</span><span class="p">(</span><span class="s1">'tuple index out of range'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">traceback</span><span class="o">.</span><span class="n">format_exception_only</span><span class="p">(</span><span class="nb">type</span><span class="p">(</span><span class="n">an_error</span><span class="p">),</span> <span class="n">an_error</span><span class="p">)</span> <span class="go">['IndexError: tuple index out of range\n']</span> </pre></div> </div> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">28.10. <code class="docutils literal notranslate"><span 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