Edit File: tokenize.html
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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"> <h1>31.7. <tt class="xref docutils literal"><span class="pre">tokenize</span></tt> — Tokenizer for Python source<a class="headerlink" href="#module-tokenize" title="Permalink to this headline">¶</a></h1> <p>The <tt class="xref docutils literal"><span class="pre">tokenize</span></tt> 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>The primary entry point is a <a class="reference external" href="../glossary.html#term-generator"><em class="xref">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 title="tokenize.generate_tokens" class="reference internal" href="#tokenize.generate_tokens"><tt class="xref 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 <tt class="xref docutils literal"><span class="pre">readline()</span></tt> method of built-in file objects (see section <a class="reference external" 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.</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 title="tokenize.tokenize" class="reference internal" href="#tokenize.tokenize"><tt class="xref 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 title="tokenize.tokenize" class="reference internal" href="#tokenize.tokenize"><tt class="xref 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 <tt class="xref docutils literal"><span class="pre">readline()</span></tt> method of built-in file objects (see section <a class="reference external" 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 title="exceptions.StopIteration" class="reference external" href="exceptions.html#exceptions.StopIteration"><tt class="xref docutils literal"><span class="pre">StopIteration</span></tt></a>.</p> <p class="versionchanged"> <span class="versionmodified">Changed in version 2.5: </span>Added <a title="exceptions.StopIteration" class="reference external" href="exceptions.html#exceptions.StopIteration"><tt class="xref 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 title="tokenize.generate_tokens" class="reference internal" href="#tokenize.generate_tokens"><tt class="xref docutils literal"><span class="pre">generate_tokens()</span></tt></a>.</p> </dd></dl> <p>All constants from the <a title="Constants representing terminal nodes of the parse tree." class="reference external" href="token.html#module-token"><tt class="xref docutils literal"><span class="pre">token</span></tt></a> module are also exported from <tt class="xref docutils literal"><span class="pre">tokenize</span></tt>, as are two additional token type values that might be passed to the <em>tokeneater</em> function by <a title="tokenize.tokenize" class="reference internal" href="#tokenize.tokenize"><tt class="xref 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>Token value used to indicate a comment.</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>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.</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 docutils literal 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 docutils literal 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 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