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<ul>
<li><a class="reference internal" href="#">pprint – Pretty-print data structures</a><ul>
<li><a class="reference internal" href="#printing">Printing</a></li>
<li><a class="reference internal" href="#formatting">Formatting</a></li>
<li><a class="reference internal" href="#arbitrary-classes">Arbitrary Classes</a></li>
<li><a class="reference internal" href="#recursion">Recursion</a></li>
<li><a class="reference internal" href="#limiting-nested-output">Limiting Nested Output</a></li>
<li><a class="reference internal" href="#controlling-output-width">Controlling Output Width</a></li>
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<div class="section" id="module-pprint">
<span id="pprint-pretty-print-data-structures"></span><h1>pprint – Pretty-print data structures<a class="headerlink" href="#module-pprint" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Purpose:</th><td class="field-body">Pretty-print data structures</td>
</tr>
<tr class="field"><th class="field-name">Python Version:</th><td class="field-body">1.4</td>
</tr>
</tbody>
</table>
<p><a class="reference internal" href="#module-pprint" title="pprint: Pretty-print data structures"><tt class="xref py py-mod docutils literal"><span class="pre">pprint</span></tt></a> contains a “pretty printer” for producing aesthetically
pleasing representations of your data structures. The formatter
produces representations of data structures that can be parsed
correctly by the interpreter, and are also easy for a human to
read. The output is kept on a single line, if possible, and indented
when split across multiple lines.</p>
<p>The examples below all depend on <tt class="docutils literal"><span class="pre">pprint_data.py</span></tt>, which contains:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">data</span> <span class="o">=</span> <span class="p">[</span> <span class="p">(</span><span class="n">i</span><span class="p">,</span> <span class="p">{</span> <span class="s">'a'</span><span class="p">:</span><span class="s">'A'</span><span class="p">,</span>
<span class="s">'b'</span><span class="p">:</span><span class="s">'B'</span><span class="p">,</span>
<span class="s">'c'</span><span class="p">:</span><span class="s">'C'</span><span class="p">,</span>
<span class="s">'d'</span><span class="p">:</span><span class="s">'D'</span><span class="p">,</span>
<span class="s">'e'</span><span class="p">:</span><span class="s">'E'</span><span class="p">,</span>
<span class="s">'f'</span><span class="p">:</span><span class="s">'F'</span><span class="p">,</span>
<span class="s">'g'</span><span class="p">:</span><span class="s">'G'</span><span class="p">,</span>
<span class="s">'h'</span><span class="p">:</span><span class="s">'H'</span><span class="p">,</span>
<span class="p">})</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">xrange</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="p">]</span>
</pre></div>
</div>
<div class="section" id="printing">
<h2>Printing<a class="headerlink" href="#printing" title="Permalink to this headline">¶</a></h2>
<p>The simplest way to use the module is through the <tt class="docutils literal"><span class="pre">pprint()</span></tt>
function. It formats your object and writes it to the data stream
passed as argument (or <a class="reference internal" href="../sys/runtime.html#sys-input-output"><em>sys.stdout</em></a> by
default).</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pprint</span>
<span class="kn">from</span> <span class="nn">pprint_data</span> <span class="kn">import</span> <span class="n">data</span>
<span class="k">print</span> <span class="s">'PRINT:'</span>
<span class="k">print</span> <span class="n">data</span>
<span class="k">print</span>
<span class="k">print</span> <span class="s">'PPRINT:'</span>
<span class="n">pprint</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python pprint_pprint.py
PRINT:
[(0, {'a': 'A', 'c': 'C', 'b': 'B', 'e': 'E', 'd': 'D', 'g': 'G', 'f': 'F', 'h': 'H'}), (1, {'a': 'A', 'c': 'C', 'b': 'B', 'e': 'E', 'd': 'D', 'g': 'G', 'f': 'F', 'h': 'H'}), (2, {'a': 'A', 'c': 'C', 'b': 'B', 'e': 'E', 'd': 'D', 'g': 'G', 'f': 'F', 'h': 'H'})]
PPRINT:
[(0,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'}),
(1,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'}),
(2,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'})]</pre>
</div>
</div>
<div class="section" id="formatting">
<h2>Formatting<a class="headerlink" href="#formatting" title="Permalink to this headline">¶</a></h2>
<p>If you need to format a data structure, but do not want to write it
directly to a stream (for logging purposes, for example) you can use
<tt class="docutils literal"><span class="pre">pformat()</span></tt> to build a string representation that can then be passed
to another function.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pformat</span>
<span class="kn">from</span> <span class="nn">pprint_data</span> <span class="kn">import</span> <span class="n">data</span>
<span class="n">logging</span><span class="o">.</span><span class="n">basicConfig</span><span class="p">(</span><span class="n">level</span><span class="o">=</span><span class="n">logging</span><span class="o">.</span><span class="n">DEBUG</span><span class="p">,</span>
<span class="n">format</span><span class="o">=</span><span class="s">'</span><span class="si">%(levelname)-8s</span><span class="s"> </span><span class="si">%(message)s</span><span class="s">'</span><span class="p">,</span>
<span class="p">)</span>
<span class="n">logging</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s">'Logging pformatted data'</span><span class="p">)</span>
<span class="n">logging</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="n">pformat</span><span class="p">(</span><span class="n">data</span><span class="p">))</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python pprint_pformat.py
DEBUG Logging pformatted data
DEBUG [(0,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'}),
(1,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'}),
(2,
{'a': 'A',
'b': 'B',
'c': 'C',
'd': 'D',
'e': 'E',
'f': 'F',
'g': 'G',
'h': 'H'})]</pre>
</div>
</div>
<div class="section" id="arbitrary-classes">
<h2>Arbitrary Classes<a class="headerlink" href="#arbitrary-classes" title="Permalink to this headline">¶</a></h2>
<p>The <tt class="docutils literal"><span class="pre">PrettyPrinter</span></tt> class used by <tt class="docutils literal"><span class="pre">pprint()</span></tt> can also work with
your own classes, if they define a <tt class="docutils literal"><span class="pre">__repr__()</span></tt> method.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pprint</span>
<span class="k">class</span> <span class="nc">node</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">contents</span><span class="o">=</span><span class="p">[]):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="n">name</span>
<span class="bp">self</span><span class="o">.</span><span class="n">contents</span> <span class="o">=</span> <span class="n">contents</span><span class="p">[:]</span>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="s">'node('</span> <span class="o">+</span> <span class="nb">repr</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">)</span> <span class="o">+</span> <span class="s">', '</span> <span class="o">+</span> <span class="nb">repr</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">contents</span><span class="p">)</span> <span class="o">+</span> <span class="s">')'</span>
<span class="n">trees</span> <span class="o">=</span> <span class="p">[</span> <span class="n">node</span><span class="p">(</span><span class="s">'node-1'</span><span class="p">),</span>
<span class="n">node</span><span class="p">(</span><span class="s">'node-2'</span><span class="p">,</span> <span class="p">[</span> <span class="n">node</span><span class="p">(</span><span class="s">'node-2-1'</span><span class="p">)]),</span>
<span class="n">node</span><span class="p">(</span><span class="s">'node-3'</span><span class="p">,</span> <span class="p">[</span> <span class="n">node</span><span class="p">(</span><span class="s">'node-3-1'</span><span class="p">)]),</span>
<span class="p">]</span>
<span class="n">pprint</span><span class="p">(</span><span class="n">trees</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python pprint_arbitrary_object.py
[node('node-1', []),
node('node-2', [node('node-2-1', [])]),
node('node-3', [node('node-3-1', [])])]</pre>
</div>
</div>
<div class="section" id="recursion">
<h2>Recursion<a class="headerlink" href="#recursion" title="Permalink to this headline">¶</a></h2>
<p>Recursive data structures are represented with a reference to the original
source of the data, with the form <tt class="docutils literal"><span class="pre"><Recursion</span> <span class="pre">on</span> <span class="pre">typename</span> <span class="pre">with</span> <span class="pre">id=number></span></tt>. For
example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pprint</span>
<span class="n">local_data</span> <span class="o">=</span> <span class="p">[</span> <span class="s">'a'</span><span class="p">,</span> <span class="s">'b'</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span> <span class="p">]</span>
<span class="n">local_data</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">local_data</span><span class="p">)</span>
<span class="k">print</span> <span class="s">'id(local_data) =>'</span><span class="p">,</span> <span class="nb">id</span><span class="p">(</span><span class="n">local_data</span><span class="p">)</span>
<span class="n">pprint</span><span class="p">(</span><span class="n">local_data</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python pprint_recursion.py
id(local_data) => 4299515952
['a', 'b', 1, 2, <Recursion on list with id=4299515952>]</pre>
</div>
</div>
<div class="section" id="limiting-nested-output">
<h2>Limiting Nested Output<a class="headerlink" href="#limiting-nested-output" title="Permalink to this headline">¶</a></h2>
<p>For very deep data structures, you may not want the output to include all of
the details. It might be impossible to format the data properly, the formatted
text might be too large to manage, or you may need all of it. In that case,
the depth argument can control how far down into the nested data structure the
pretty printer goes.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pprint</span>
<span class="kn">from</span> <span class="nn">pprint_data</span> <span class="kn">import</span> <span class="n">data</span>
<span class="n">pprint</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="n">depth</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
</pre></div>
</div>
<div class="highlight-python"><pre>$ python pprint_depth.py
[(...), (...), (...)]</pre>
</div>
</div>
<div class="section" id="controlling-output-width">
<h2>Controlling Output Width<a class="headerlink" href="#controlling-output-width" title="Permalink to this headline">¶</a></h2>
<p>The default output width for the formatted text is 80 columns. To adjust that
width, use the width argument to <tt class="docutils literal"><span class="pre">pprint()</span></tt>.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">pprint</span> <span class="kn">import</span> <span class="n">pprint</span>
<span class="kn">from</span> <span class="nn">pprint_data</span> <span class="kn">import</span> <span class="n">data</span>
<span class="k">for</span> <span class="n">d</span> <span class="ow">in</span> <span class="n">data</span><span class="p">:</span>
<span class="k">for</span> <span class="n">c</span> <span class="ow">in</span> <span class="s">'defgh'</span><span class="p">:</span>
<span class="k">del</span> <span class="n">d</span><span class="p">[</span><span class="mi">1</span><span class="p">][</span><span class="n">c</span><span class="p">]</span>
<span class="k">for</span> <span class="n">width</span> <span class="ow">in</span> <span class="p">[</span> <span class="mi">80</span><span class="p">,</span> <span class="mi">20</span><span class="p">,</span> <span class="mi">5</span> <span class="p">]:</span>
<span class="k">print</span> <span class="s">'WIDTH ='</span><span class="p">,</span> <span class="n">width</span>
<span class="n">pprint</span><span class="p">(</span><span class="n">data</span><span class="p">,</span> <span class="n">width</span><span class="o">=</span><span class="n">width</span><span class="p">)</span>
<span class="k">print</span>
</pre></div>
</div>
<p>Notice that when the width is too low to accommodate the formatted data
structure, the lines are not truncated or wrapped if that would introduce
invalid syntax.</p>
<div class="highlight-python"><pre>$ python pprint_width.py
WIDTH = 80
[(0, {'a': 'A', 'b': 'B', 'c': 'C'}),
(1, {'a': 'A', 'b': 'B', 'c': 'C'}),
(2, {'a': 'A', 'b': 'B', 'c': 'C'})]
WIDTH = 20
[(0,
{'a': 'A',
'b': 'B',
'c': 'C'}),
(1,
{'a': 'A',
'b': 'B',
'c': 'C'}),
(2,
{'a': 'A',
'b': 'B',
'c': 'C'})]
WIDTH = 5
[(0,
{'a': 'A',
'b': 'B',
'c': 'C'}),
(1,
{'a': 'A',
'b': 'B',
'c': 'C'}),
(2,
{'a': 'A',
'b': 'B',
'c': 'C'})]</pre>
</div>
<div class="admonition-see-also admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt><a class="reference external" href="http://docs.python.org/lib/module-pprint.html">pprint</a></dt>
<dd>Standard library documentation for this module.</dd>
</dl>
</div>
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