Edit File: tokenize.html
<!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="Content-Type" content="text/html; charset=utf-8" /> <title>31.7. tokenize — Tokenizer for Python source — Python 2.7.5 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </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 2.7.5 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python 2.7.5 documentation" href="../index.html" /> <link rel="up" title="31. Python Language Services" href="language.html" /> <link rel="next" title="31.8. tabnanny — Detection of ambiguous indentation" href="tabnanny.html" /> <link rel="prev" title="31.6. keyword — Testing for Python keywords" href="keyword.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head> <body> <div class="related"> <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="tabnanny.html" title="31.8. tabnanny — Detection of ambiguous indentation" accesskey="N">next</a> |</li> <li class="right" > <a href="keyword.html" title="31.6. keyword — Testing for Python keywords" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="language.html" accesskey="U">31. Python Language Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-tokenize"> <span id="tokenize-tokenizer-for-python-source"></span><h1>31.7. <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-mod docutils literal"><span class="pre">tokenize</span></tt></a> — Tokenizer for Python source<a class="headerlink" href="#module-tokenize" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="http://hg.python.org/cpython/file/2.7/Lib/tokenize.py">Lib/tokenize.py</a></p> <hr class="docutils" /> <p>The <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-mod docutils literal"><span class="pre">tokenize</span></tt></a> module provides a lexical scanner for Python source code, implemented in Python. The scanner in this module returns comments as tokens as well, making it useful for implementing “pretty-printers,” including colorizers for on-screen displays.</p> <p>To simplify token stream handling, all <a class="reference internal" href="../reference/lexical_analysis.html#operators"><em>Operators</em></a> and <a class="reference internal" href="../reference/lexical_analysis.html#delimiters"><em>Delimiters</em></a> tokens are returned using the generic <a class="reference internal" href="token.html#token.OP" title="token.OP"><tt class="xref py py-data docutils literal"><span class="pre">token.OP</span></tt></a> token type. The exact type can be determined by checking the token <tt class="docutils literal"><span class="pre">string</span></tt> field on the <a class="reference internal" href="../glossary.html#term-named-tuple"><em class="xref std std-term">named tuple</em></a> returned from <a class="reference internal" href="#tokenize.tokenize" title="tokenize.tokenize"><tt class="xref py py-func docutils literal"><span class="pre">tokenize.tokenize()</span></tt></a> for the character sequence that identifies a specific operator token.</p> <p>The primary entry point is a <a class="reference internal" href="../glossary.html#term-generator"><em class="xref std std-term">generator</em></a>:</p> <dl class="function"> <dt id="tokenize.generate_tokens"> <tt class="descclassname">tokenize.</tt><tt class="descname">generate_tokens</tt><big>(</big><em>readline</em><big>)</big><a class="headerlink" href="#tokenize.generate_tokens" title="Permalink to this definition">¶</a></dt> <dd><p>The <a class="reference internal" href="#tokenize.generate_tokens" title="tokenize.generate_tokens"><tt class="xref py py-func docutils literal"><span class="pre">generate_tokens()</span></tt></a> generator requires one argument, <em>readline</em>, which must be a callable object which provides the same interface as the <a class="reference internal" href="readline.html#module-readline" title="readline: GNU readline support for Python. (Unix)"><tt class="xref py py-meth docutils literal"><span class="pre">readline()</span></tt></a> method of built-in file objects (see section <a class="reference internal" href="stdtypes.html#bltin-file-objects"><em>File Objects</em></a>). Each call to the function should return one line of input as a string. Alternately, <em>readline</em> may be a callable object that signals completion by raising <a class="reference internal" href="exceptions.html#exceptions.StopIteration" title="exceptions.StopIteration"><tt class="xref py py-exc docutils literal"><span class="pre">StopIteration</span></tt></a>.</p> <p>The generator produces 5-tuples with these members: the token type; the token string; a 2-tuple <tt class="docutils literal"><span class="pre">(srow,</span> <span class="pre">scol)</span></tt> of ints specifying the row and column where the token begins in the source; a 2-tuple <tt class="docutils literal"><span class="pre">(erow,</span> <span class="pre">ecol)</span></tt> of ints specifying the row and column where the token ends in the source; and the line on which the token was found. The line passed (the last tuple item) is the <em>logical</em> line; continuation lines are included.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.2.</span></p> </dd></dl> <p>An older entry point is retained for backward compatibility:</p> <dl class="function"> <dt id="tokenize.tokenize"> <tt class="descclassname">tokenize.</tt><tt class="descname">tokenize</tt><big>(</big><em>readline</em><span class="optional">[</span>, <em>tokeneater</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#tokenize.tokenize" title="Permalink to this definition">¶</a></dt> <dd><p>The <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-func docutils literal"><span class="pre">tokenize()</span></tt></a> function accepts two parameters: one representing the input stream, and one providing an output mechanism for <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-func docutils literal"><span class="pre">tokenize()</span></tt></a>.</p> <p>The first parameter, <em>readline</em>, must be a callable object which provides the same interface as the <a class="reference internal" href="readline.html#module-readline" title="readline: GNU readline support for Python. (Unix)"><tt class="xref py py-meth docutils literal"><span class="pre">readline()</span></tt></a> method of built-in file objects (see section <a class="reference internal" href="stdtypes.html#bltin-file-objects"><em>File Objects</em></a>). Each call to the function should return one line of input as a string. Alternately, <em>readline</em> may be a callable object that signals completion by raising <a class="reference internal" href="exceptions.html#exceptions.StopIteration" title="exceptions.StopIteration"><tt class="xref py py-exc docutils literal"><span class="pre">StopIteration</span></tt></a>.</p> <p class="versionchanged"> <span class="versionmodified">Changed in version 2.5: </span>Added <a class="reference internal" href="exceptions.html#exceptions.StopIteration" title="exceptions.StopIteration"><tt class="xref py py-exc docutils literal"><span class="pre">StopIteration</span></tt></a> support.</p> <p>The second parameter, <em>tokeneater</em>, must also be a callable object. It is called once for each token, with five arguments, corresponding to the tuples generated by <a class="reference internal" href="#tokenize.generate_tokens" title="tokenize.generate_tokens"><tt class="xref py py-func docutils literal"><span class="pre">generate_tokens()</span></tt></a>.</p> </dd></dl> <p>All constants from the <a class="reference internal" href="token.html#module-token" title="token: Constants representing terminal nodes of the parse tree."><tt class="xref py py-mod docutils literal"><span class="pre">token</span></tt></a> module are also exported from <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-mod docutils literal"><span class="pre">tokenize</span></tt></a>, as are two additional token type values that might be passed to the <em>tokeneater</em> function by <a class="reference internal" href="#module-tokenize" title="tokenize: Lexical scanner for Python source code."><tt class="xref py py-func docutils literal"><span class="pre">tokenize()</span></tt></a>:</p> <dl class="data"> <dt id="tokenize.COMMENT"> <tt class="descclassname">tokenize.</tt><tt class="descname">COMMENT</tt><a class="headerlink" href="#tokenize.COMMENT" title="Permalink to this definition">¶</a></dt> <dd><p>Token value used to indicate a comment.</p> </dd></dl> <dl class="data"> <dt id="tokenize.NL"> <tt class="descclassname">tokenize.</tt><tt class="descname">NL</tt><a class="headerlink" href="#tokenize.NL" title="Permalink to this definition">¶</a></dt> <dd><p>Token value used to indicate a non-terminating newline. The NEWLINE token indicates the end of a logical line of Python code; NL tokens are generated when a logical line of code is continued over multiple physical lines.</p> </dd></dl> <p>Another function is provided to reverse the tokenization process. This is useful for creating tools that tokenize a script, modify the token stream, and write back the modified script.</p> <dl class="function"> <dt id="tokenize.untokenize"> <tt class="descclassname">tokenize.</tt><tt class="descname">untokenize</tt><big>(</big><em>iterable</em><big>)</big><a class="headerlink" href="#tokenize.untokenize" title="Permalink to this definition">¶</a></dt> <dd><p>Converts tokens back into Python source code. The <em>iterable</em> must return sequences with at least two elements, the token type and the token string. Any additional sequence elements are ignored.</p> <p>The reconstructed script is returned as a single string. The result is guaranteed to tokenize back to match the input so that the conversion is lossless and round-trips are assured. The guarantee applies only to the token type and token string as the spacing between tokens (column positions) may change.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.5.</span></p> </dd></dl> <p>Example of a script re-writer that transforms float literals into Decimal objects:</p> <div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">decistmt</span><span class="p">(</span><span class="n">s</span><span class="p">):</span> <span class="sd">"""Substitute Decimals for floats in a string of statements.</span> <span class="sd"> >>> from decimal import Decimal</span> <span class="sd"> >>> s = 'print +21.3e-5*-.1234/81.7'</span> <span class="sd"> >>> decistmt(s)</span> <span class="sd"> "print +Decimal ('21.3e-5')*-Decimal ('.1234')/Decimal ('81.7')"</span> <span class="sd"> >>> exec(s)</span> <span class="sd"> -3.21716034272e-007</span> <span class="sd"> >>> exec(decistmt(s))</span> <span class="sd"> -3.217160342717258261933904529E-7</span> <span class="sd"> """</span> <span class="n">result</span> <span class="o">=</span> <span class="p">[]</span> <span class="n">g</span> <span class="o">=</span> <span class="n">generate_tokens</span><span class="p">(</span><span class="n">StringIO</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="o">.</span><span class="n">readline</span><span class="p">)</span> <span class="c"># tokenize the string</span> <span class="k">for</span> <span class="n">toknum</span><span class="p">,</span> <span class="n">tokval</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">_</span> <span class="ow">in</span> <span class="n">g</span><span class="p">:</span> <span class="k">if</span> <span class="n">toknum</span> <span class="o">==</span> <span class="n">NUMBER</span> <span class="ow">and</span> <span class="s">'.'</span> <span class="ow">in</span> <span class="n">tokval</span><span class="p">:</span> <span class="c"># replace NUMBER tokens</span> <span class="n">result</span><span class="o">.</span><span class="n">extend</span><span class="p">([</span> <span class="p">(</span><span class="n">NAME</span><span class="p">,</span> <span class="s">'Decimal'</span><span class="p">),</span> <span class="p">(</span><span class="n">OP</span><span class="p">,</span> <span class="s">'('</span><span class="p">),</span> <span class="p">(</span><span class="n">STRING</span><span class="p">,</span> <span class="nb">repr</span><span class="p">(</span><span class="n">tokval</span><span class="p">)),</span> <span class="p">(</span><span class="n">OP</span><span class="p">,</span> <span class="s">')'</span><span class="p">)</span> <span class="p">])</span> <span class="k">else</span><span class="p">:</span> <span class="n">result</span><span class="o">.</span><span class="n">append</span><span class="p">((</span><span class="n">toknum</span><span class="p">,</span> <span class="n">tokval</span><span class="p">))</span> <span class="k">return</span> <span class="n">untokenize</span><span class="p">(</span><span class="n">result</span><span class="p">)</span> </pre></div> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="keyword.html" title="previous chapter">31.6. <tt class="docutils literal"><span class="pre">keyword</span></tt> — Testing for Python keywords</a></p> <h4>Next topic</h4> <p class="topless"><a href="tabnanny.html" title="next chapter">31.8. <tt class="docutils literal"><span class="pre">tabnanny</span></tt> — Detection of ambiguous indentation</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/library/tokenize.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="tabnanny.html" title="31.8. tabnanny — Detection of ambiguous indentation" >next</a> |</li> <li class="right" > <a href="keyword.html" title="31.6. keyword — Testing for Python keywords" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >The Python Standard Library</a> »</li> <li><a href="language.html" >31. Python Language Services</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="http://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>