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Internet Data Handling</a> &#187;</li> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" 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> </div> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="module-json"> <span id="json-json-encoder-and-decoder"></span><h1>19.2. <a class="reference internal" href="#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> — JSON encoder and decoder<a class="headerlink" href="#module-json" title="Permalink to this headline">¶</a></h1> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.6/Lib/json/__init__.py">Lib/json/__init__.py</a></p> <hr class="docutils" /> <p><a class="reference external" href="http://json.org">JSON (JavaScript Object Notation)</a>, specified by <span class="target" id="index-0"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc7159.html"><strong>RFC 7159</strong></a> (which obsoletes <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc4627.html"><strong>RFC 4627</strong></a>) and by <a class="reference external" href="http://www.ecma-international.org/publications/standards/Ecma-404.htm">ECMA-404</a>, is a lightweight data interchange format inspired by <a class="reference external" href="https://en.wikipedia.org/wiki/JavaScript">JavaScript</a> object literal syntax (although it is not a strict subset of JavaScript <a class="footnote-reference" href="#rfc-errata" id="id1">[1]</a> ).</p> <p><a class="reference internal" href="#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> exposes an API familiar to users of the standard library <a class="reference internal" href="marshal.html#module-marshal" title="marshal: Convert Python objects to streams of bytes and back (with different constraints)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">marshal</span></code></a> and <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> modules.</p> <p>Encoding basic Python object hierarchies:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">([</span><span class="s1">&#39;foo&#39;</span><span class="p">,</span> <span class="p">{</span><span class="s1">&#39;bar&#39;</span><span class="p">:</span> <span class="p">(</span><span class="s1">&#39;baz&#39;</span><span class="p">,</span> <span class="kc">None</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="mi">2</span><span class="p">)}])</span> <span class="go">&#39;[&quot;foo&quot;, {&quot;bar&quot;: [&quot;baz&quot;, null, 1.0, 2]}]&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="s2">&quot;</span><span class="se">\&quot;</span><span class="s2">foo</span><span class="se">\b</span><span class="s2">ar&quot;</span><span class="p">))</span> <span class="go">&quot;\&quot;foo\bar&quot;</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="s1">&#39;</span><span class="se">\u1234</span><span class="s1">&#39;</span><span class="p">))</span> <span class="go">&quot;\u1234&quot;</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="s1">&#39;</span><span class="se">\\</span><span class="s1">&#39;</span><span class="p">))</span> <span class="go">&quot;\\&quot;</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">({</span><span class="s2">&quot;c&quot;</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span> <span class="s2">&quot;b&quot;</span><span class="p">:</span> <span class="mi">0</span><span class="p">,</span> <span class="s2">&quot;a&quot;</span><span class="p">:</span> <span class="mi">0</span><span class="p">},</span> <span class="n">sort_keys</span><span class="o">=</span><span class="kc">True</span><span class="p">))</span> <span class="go">{&quot;a&quot;: 0, &quot;b&quot;: 0, &quot;c&quot;: 0}</span> <span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">io</span> <span class="k">import</span> <span class="n">StringIO</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">io</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">()</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dump</span><span class="p">([</span><span class="s1">&#39;streaming API&#39;</span><span class="p">],</span> <span class="n">io</span><span class="p">)</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">io</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span> <span class="go">&#39;[&quot;streaming API&quot;]&#39;</span> </pre></div> </div> <p>Compact encoding:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dumps</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="mi">3</span><span class="p">,</span> <span class="p">{</span><span class="s1">&#39;4&#39;</span><span class="p">:</span> <span class="mi">5</span><span class="p">,</span> <span class="s1">&#39;6&#39;</span><span class="p">:</span> <span class="mi">7</span><span class="p">}],</span> <span class="n">separators</span><span class="o">=</span><span class="p">(</span><span class="s1">&#39;,&#39;</span><span class="p">,</span> <span class="s1">&#39;:&#39;</span><span class="p">))</span> <span class="go">&#39;[1,2,3,{&quot;4&quot;:5,&quot;6&quot;:7}]&#39;</span> </pre></div> </div> <p>Pretty printing:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">({</span><span class="s1">&#39;4&#39;</span><span class="p">:</span> <span class="mi">5</span><span class="p">,</span> <span class="s1">&#39;6&#39;</span><span class="p">:</span> <span class="mi">7</span><span class="p">},</span> <span class="n">sort_keys</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">indent</span><span class="o">=</span><span class="mi">4</span><span class="p">))</span> <span class="go">{</span> <span class="go"> &quot;4&quot;: 5,</span> <span class="go"> &quot;6&quot;: 7</span> <span class="go">}</span> </pre></div> </div> <p>Decoding JSON:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;[&quot;foo&quot;, {&quot;bar&quot;:[&quot;baz&quot;, null, 1.0, 2]}]&#39;</span><span class="p">)</span> <span class="go">[&#39;foo&#39;, {&#39;bar&#39;: [&#39;baz&#39;, None, 1.0, 2]}]</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;&quot;</span><span class="se">\\</span><span class="s1">&quot;foo</span><span class="se">\\</span><span class="s1">bar&quot;&#39;</span><span class="p">)</span> <span class="go">&#39;&quot;foo\x08ar&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">io</span> <span class="k">import</span> <span class="n">StringIO</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">io</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="s1">&#39;[&quot;streaming API&quot;]&#39;</span><span class="p">)</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">load</span><span class="p">(</span><span class="n">io</span><span class="p">)</span> <span class="go">[&#39;streaming API&#39;]</span> </pre></div> </div> <p>Specializing JSON object decoding:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="k">def</span> <span class="nf">as_complex</span><span class="p">(</span><span class="n">dct</span><span class="p">):</span> <span class="gp">... </span> <span class="k">if</span> <span class="s1">&#39;__complex__&#39;</span> <span class="ow">in</span> <span class="n">dct</span><span class="p">:</span> <span class="gp">... </span> <span class="k">return</span> <span class="nb">complex</span><span class="p">(</span><span class="n">dct</span><span class="p">[</span><span class="s1">&#39;real&#39;</span><span class="p">],</span> <span class="n">dct</span><span class="p">[</span><span class="s1">&#39;imag&#39;</span><span class="p">])</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">dct</span> <span class="gp">...</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;{&quot;__complex__&quot;: true, &quot;real&quot;: 1, &quot;imag&quot;: 2}&#39;</span><span class="p">,</span> <span class="gp">... </span> <span class="n">object_hook</span><span class="o">=</span><span class="n">as_complex</span><span class="p">)</span> <span class="go">(1+2j)</span> <span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">decimal</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;1.1&#39;</span><span class="p">,</span> <span class="n">parse_float</span><span class="o">=</span><span class="n">decimal</span><span class="o">.</span><span class="n">Decimal</span><span class="p">)</span> <span class="go">Decimal(&#39;1.1&#39;)</span> </pre></div> </div> <p>Extending <a class="reference internal" href="#json.JSONEncoder" title="json.JSONEncoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONEncoder</span></code></a>:</p> <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="nn">json</span> <span class="gp">&gt;&gt;&gt; </span><span class="k">class</span> <span class="nc">ComplexEncoder</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">JSONEncoder</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">default</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">):</span> <span class="gp">... </span> <span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="nb">complex</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="p">[</span><span class="n">obj</span><span class="o">.</span><span class="n">real</span><span class="p">,</span> <span class="n">obj</span><span class="o">.</span><span class="n">imag</span><span class="p">]</span> <span class="gp">... </span> <span class="c1"># Let the base class default method raise the TypeError</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">json</span><span class="o">.</span><span class="n">JSONEncoder</span><span class="o">.</span><span class="n">default</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">)</span> <span class="gp">...</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="mi">2</span> <span class="o">+</span> <span class="mi">1</span><span class="n">j</span><span class="p">,</span> <span class="bp">cls</span><span class="o">=</span><span class="n">ComplexEncoder</span><span class="p">)</span> <span class="go">&#39;[2.0, 1.0]&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">ComplexEncoder</span><span class="p">()</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="mi">2</span> <span class="o">+</span> <span class="mi">1</span><span class="n">j</span><span class="p">)</span> <span class="go">&#39;[2.0, 1.0]&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="nb">list</span><span class="p">(</span><span class="n">ComplexEncoder</span><span class="p">()</span><span class="o">.</span><span class="n">iterencode</span><span class="p">(</span><span class="mi">2</span> <span class="o">+</span> <span class="mi">1</span><span class="n">j</span><span class="p">))</span> <span class="go">[&#39;[2.0&#39;, &#39;, 1.0&#39;, &#39;]&#39;]</span> </pre></div> </div> <p>Using <a class="reference internal" href="#module-json.tool" title="json.tool: A command line to validate and pretty-print JSON."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json.tool</span></code></a> from the shell to validate and pretty-print:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> <span class="nb">echo</span> <span class="s1">&#39;{&quot;json&quot;:&quot;obj&quot;}&#39;</span> <span class="p">|</span> python -m json.tool <span class="go">{</span> <span class="go"> &quot;json&quot;: &quot;obj&quot;</span> <span class="go">}</span> <span class="gp">$</span> <span class="nb">echo</span> <span class="s1">&#39;{1.2:3.4}&#39;</span> <span class="p">|</span> python -m json.tool <span class="go">Expecting property name enclosed in double quotes: line 1 column 2 (char 1)</span> </pre></div> </div> <p>See <a class="reference internal" href="#json-commandline"><span class="std std-ref">Command Line Interface</span></a> for detailed documentation.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">JSON is a subset of <a class="reference external" href="http://yaml.org/">YAML</a> 1.2. The JSON produced by this module’s default settings (in particular, the default <em>separators</em> value) is also a subset of YAML 1.0 and 1.1. This module can thus also be used as a YAML serializer.</p> </div> <div class="section" id="basic-usage"> <h2>19.2.1. Basic Usage<a class="headerlink" href="#basic-usage" title="Permalink to this headline">¶</a></h2> <dl class="function"> <dt id="json.dump"> <code class="descclassname">json.</code><code class="descname">dump</code><span class="sig-paren">(</span><em>obj</em>, <em>fp</em>, <em>*</em>, <em>skipkeys=False</em>, <em>ensure_ascii=True</em>, <em>check_circular=True</em>, <em>allow_nan=True</em>, <em>cls=None</em>, <em>indent=None</em>, <em>separators=None</em>, <em>default=None</em>, <em>sort_keys=False</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#json.dump" title="Permalink to this definition">¶</a></dt> <dd><p>Serialize <em>obj</em> as a JSON formatted stream to <em>fp</em> (a <code class="docutils literal notranslate"><span class="pre">.write()</span></code>-supporting <a class="reference internal" href="../glossary.html#term-file-like-object"><span class="xref std std-term">file-like object</span></a>) using this <a class="reference internal" href="#py-to-json-table"><span class="std std-ref">conversion table</span></a>.</p> <p>If <em>skipkeys</em> is true (default: <code class="docutils literal notranslate"><span class="pre">False</span></code>), then dict keys that are not of a basic type (<a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, <a class="reference internal" href="functions.html#bool" title="bool"><code class="xref py py-class docutils literal notranslate"><span class="pre">bool</span></code></a>, <code class="docutils literal notranslate"><span class="pre">None</span></code>) will be skipped instead of raising a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> <p>The <a class="reference internal" href="#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> module always produces <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> objects, not <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects. Therefore, <code class="docutils literal notranslate"><span class="pre">fp.write()</span></code> must support <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> input.</p> <p>If <em>ensure_ascii</em> is true (the default), the output is guaranteed to have all incoming non-ASCII characters escaped. If <em>ensure_ascii</em> is false, these characters will be output as-is.</p> <p>If <em>check_circular</em> is false (default: <code class="docutils literal notranslate"><span class="pre">True</span></code>), then the circular reference check for container types will be skipped and a circular reference will result in an <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a> (or worse).</p> <p>If <em>allow_nan</em> is false (default: <code class="docutils literal notranslate"><span class="pre">True</span></code>), then it will be a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> to serialize out of range <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> values (<code class="docutils literal notranslate"><span class="pre">nan</span></code>, <code class="docutils literal notranslate"><span class="pre">inf</span></code>, <code class="docutils literal notranslate"><span class="pre">-inf</span></code>) in strict compliance of the JSON specification. If <em>allow_nan</em> is true, their JavaScript equivalents (<code class="docutils literal notranslate"><span class="pre">NaN</span></code>, <code class="docutils literal notranslate"><span class="pre">Infinity</span></code>, <code class="docutils literal notranslate"><span class="pre">-Infinity</span></code>) will be used.</p> <p>If <em>indent</em> is a non-negative integer or string, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0, negative, or <code class="docutils literal notranslate"><span class="pre">&quot;&quot;</span></code> will only insert newlines. <code class="docutils literal notranslate"><span class="pre">None</span></code> (the default) selects the most compact representation. Using a positive integer indent indents that many spaces per level. If <em>indent</em> is a string (such as <code class="docutils literal notranslate"><span class="pre">&quot;\t&quot;</span></code>), that string is used to indent each level.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span>Allow strings for <em>indent</em> in addition to integers.</p> </div> <p>If specified, <em>separators</em> should be an <code class="docutils literal notranslate"><span class="pre">(item_separator,</span> <span class="pre">key_separator)</span></code> tuple. The default is <code class="docutils literal notranslate"><span class="pre">(',</span> <span class="pre">',</span> <span class="pre">':</span> <span class="pre">')</span></code> if <em>indent</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code> and <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':</span> <span class="pre">')</span></code> otherwise. To get the most compact JSON representation, you should specify <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':')</span></code> to eliminate whitespace.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.4: </span>Use <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':</span> <span class="pre">')</span></code> as default if <em>indent</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </div> <p>If specified, <em>default</em> should be a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>. If not specified, <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> is raised.</p> <p>If <em>sort_keys</em> is true (default: <code class="docutils literal notranslate"><span class="pre">False</span></code>), then the output of dictionaries will be sorted by key.</p> <p>To use a custom <a class="reference internal" href="#json.JSONEncoder" title="json.JSONEncoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONEncoder</span></code></a> subclass (e.g. one that overrides the <code class="xref py py-meth docutils literal notranslate"><span class="pre">default()</span></code> method to serialize additional types), specify it with the <em>cls</em> kwarg; otherwise <a class="reference internal" href="#json.JSONEncoder" title="json.JSONEncoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONEncoder</span></code></a> is used.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>All optional parameters are now <a class="reference internal" href="../glossary.html#keyword-only-parameter"><span class="std std-ref">keyword-only</span></a>.</p> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Unlike <a class="reference internal" href="pickle.html#module-pickle" title="pickle: Convert Python objects to streams of bytes and back."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pickle</span></code></a> and <a class="reference internal" href="marshal.html#module-marshal" title="marshal: Convert Python objects to streams of bytes and back (with different constraints)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">marshal</span></code></a>, JSON is not a framed protocol, so trying to serialize multiple objects with repeated calls to <a class="reference internal" href="#json.dump" title="json.dump"><code class="xref py py-func docutils literal notranslate"><span class="pre">dump()</span></code></a> using the same <em>fp</em> will result in an invalid JSON file.</p> </div> </dd></dl> <dl class="function"> <dt id="json.dumps"> <code class="descclassname">json.</code><code class="descname">dumps</code><span class="sig-paren">(</span><em>obj</em>, <em>*</em>, <em>skipkeys=False</em>, <em>ensure_ascii=True</em>, <em>check_circular=True</em>, <em>allow_nan=True</em>, <em>cls=None</em>, <em>indent=None</em>, <em>separators=None</em>, <em>default=None</em>, <em>sort_keys=False</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#json.dumps" title="Permalink to this definition">¶</a></dt> <dd><p>Serialize <em>obj</em> to a JSON formatted <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> using this <a class="reference internal" href="#py-to-json-table"><span class="std std-ref">conversion table</span></a>. The arguments have the same meaning as in <a class="reference internal" href="#json.dump" title="json.dump"><code class="xref py py-func docutils literal notranslate"><span class="pre">dump()</span></code></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Keys in key/value pairs of JSON are always of the type <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>. When a dictionary is converted into JSON, all the keys of the dictionary are coerced to strings. As a result of this, if a dictionary is converted into JSON and then back into a dictionary, the dictionary may not equal the original one. That is, <code class="docutils literal notranslate"><span class="pre">loads(dumps(x))</span> <span class="pre">!=</span> <span class="pre">x</span></code> if x has non-string keys.</p> </div> </dd></dl> <dl class="function"> <dt id="json.load"> <code class="descclassname">json.</code><code class="descname">load</code><span class="sig-paren">(</span><em>fp</em>, <em>*</em>, <em>cls=None</em>, <em>object_hook=None</em>, <em>parse_float=None</em>, <em>parse_int=None</em>, <em>parse_constant=None</em>, <em>object_pairs_hook=None</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#json.load" title="Permalink to this definition">¶</a></dt> <dd><p>Deserialize <em>fp</em> (a <code class="docutils literal notranslate"><span class="pre">.read()</span></code>-supporting <a class="reference internal" href="../glossary.html#term-text-file"><span class="xref std std-term">text file</span></a> or <a class="reference internal" href="../glossary.html#term-binary-file"><span class="xref std std-term">binary file</span></a> containing a JSON document) to a Python object using this <a class="reference internal" href="#json-to-py-table"><span class="std std-ref">conversion table</span></a>.</p> <p><em>object_hook</em> is an optional function that will be called with the result of any object literal decoded (a <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>). The return value of <em>object_hook</em> will be used instead of the <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>. This feature can be used to implement custom decoders (e.g. <a class="reference external" href="http://www.jsonrpc.org">JSON-RPC</a> class hinting).</p> <p><em>object_pairs_hook</em> is an optional function that will be called with the result of any object literal decoded with an ordered list of pairs. The return value of <em>object_pairs_hook</em> will be used instead of the <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, <a class="reference internal" href="collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.OrderedDict()</span></code></a> will remember the order of insertion). If <em>object_hook</em> is also defined, the <em>object_pairs_hook</em> takes priority.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span>Added support for <em>object_pairs_hook</em>.</p> </div> <p><em>parse_float</em>, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to <code class="docutils literal notranslate"><span class="pre">float(num_str)</span></code>. This can be used to use another datatype or parser for JSON floats (e.g. <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>).</p> <p><em>parse_int</em>, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to <code class="docutils literal notranslate"><span class="pre">int(num_str)</span></code>. This can be used to use another datatype or parser for JSON integers (e.g. <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>).</p> <p><em>parse_constant</em>, if specified, will be called with one of the following strings: <code class="docutils literal notranslate"><span class="pre">'-Infinity'</span></code>, <code class="docutils literal notranslate"><span class="pre">'Infinity'</span></code>, <code class="docutils literal notranslate"><span class="pre">'NaN'</span></code>. This can be used to raise an exception if invalid JSON numbers are encountered.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span><em>parse_constant</em> doesn’t get called on ‘null’, ‘true’, ‘false’ anymore.</p> </div> <p>To use a custom <a class="reference internal" href="#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONDecoder</span></code></a> subclass, specify it with the <code class="docutils literal notranslate"><span class="pre">cls</span></code> kwarg; otherwise <a class="reference internal" href="#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONDecoder</span></code></a> is used. Additional keyword arguments will be passed to the constructor of the class.</p> <p>If the data being deserialized is not a valid JSON document, a <a class="reference internal" href="#json.JSONDecodeError" title="json.JSONDecodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">JSONDecodeError</span></code></a> will be raised.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>All optional parameters are now <a class="reference internal" href="../glossary.html#keyword-only-parameter"><span class="std std-ref">keyword-only</span></a>.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span><em>fp</em> can now be a <a class="reference internal" href="../glossary.html#term-binary-file"><span class="xref std std-term">binary file</span></a>. The input encoding should be UTF-8, UTF-16 or UTF-32.</p> </div> </dd></dl> <dl class="function"> <dt id="json.loads"> <code class="descclassname">json.</code><code class="descname">loads</code><span class="sig-paren">(</span><em>s</em>, <em>*</em>, <em>encoding=None</em>, <em>cls=None</em>, <em>object_hook=None</em>, <em>parse_float=None</em>, <em>parse_int=None</em>, <em>parse_constant=None</em>, <em>object_pairs_hook=None</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#json.loads" title="Permalink to this definition">¶</a></dt> <dd><p>Deserialize <em>s</em> (a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> instance containing a JSON document) to a Python object using this <a class="reference internal" href="#json-to-py-table"><span class="std std-ref">conversion table</span></a>.</p> <p>The other arguments have the same meaning as in <a class="reference internal" href="#json.load" title="json.load"><code class="xref py py-func docutils literal notranslate"><span class="pre">load()</span></code></a>, except <em>encoding</em> which is ignored and deprecated.</p> <p>If the data being deserialized is not a valid JSON document, a <a class="reference internal" href="#json.JSONDecodeError" title="json.JSONDecodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">JSONDecodeError</span></code></a> will be raised.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span><em>s</em> can now be of type <a class="reference internal" href="stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>. The input encoding should be UTF-8, UTF-16 or UTF-32.</p> </div> </dd></dl> </div> <div class="section" id="encoders-and-decoders"> <h2>19.2.2. Encoders and Decoders<a class="headerlink" href="#encoders-and-decoders" title="Permalink to this headline">¶</a></h2> <dl class="class"> <dt id="json.JSONDecoder"> <em class="property">class </em><code class="descclassname">json.</code><code class="descname">JSONDecoder</code><span class="sig-paren">(</span><em>*</em>, <em>object_hook=None</em>, <em>parse_float=None</em>, <em>parse_int=None</em>, <em>parse_constant=None</em>, <em>strict=True</em>, <em>object_pairs_hook=None</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONDecoder" title="Permalink to this definition">¶</a></dt> <dd><p>Simple JSON decoder.</p> <p>Performs the following translations in decoding by default:</p> <table border="1" class="docutils" id="json-to-py-table"> <colgroup> <col width="44%" /> <col width="56%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">JSON</th> <th class="head">Python</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td>object</td> <td>dict</td> </tr> <tr class="row-odd"><td>array</td> <td>list</td> </tr> <tr class="row-even"><td>string</td> <td>str</td> </tr> <tr class="row-odd"><td>number (int)</td> <td>int</td> </tr> <tr class="row-even"><td>number (real)</td> <td>float</td> </tr> <tr class="row-odd"><td>true</td> <td>True</td> </tr> <tr class="row-even"><td>false</td> <td>False</td> </tr> <tr class="row-odd"><td>null</td> <td>None</td> </tr> </tbody> </table> <p>It also understands <code class="docutils literal notranslate"><span class="pre">NaN</span></code>, <code class="docutils literal notranslate"><span class="pre">Infinity</span></code>, and <code class="docutils literal notranslate"><span class="pre">-Infinity</span></code> as their corresponding <code class="docutils literal notranslate"><span class="pre">float</span></code> values, which is outside the JSON spec.</p> <p><em>object_hook</em>, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting).</p> <p><em>object_pairs_hook</em>, if specified will be called with the result of every JSON object decoded with an ordered list of pairs. The return value of <em>object_pairs_hook</em> will be used instead of the <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, <a class="reference internal" href="collections.html#collections.OrderedDict" title="collections.OrderedDict"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.OrderedDict()</span></code></a> will remember the order of insertion). If <em>object_hook</em> is also defined, the <em>object_pairs_hook</em> takes priority.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span>Added support for <em>object_pairs_hook</em>.</p> </div> <p><em>parse_float</em>, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to <code class="docutils literal notranslate"><span class="pre">float(num_str)</span></code>. This can be used to use another datatype or parser for JSON floats (e.g. <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>).</p> <p><em>parse_int</em>, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to <code class="docutils literal notranslate"><span class="pre">int(num_str)</span></code>. This can be used to use another datatype or parser for JSON integers (e.g. <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>).</p> <p><em>parse_constant</em>, if specified, will be called with one of the following strings: <code class="docutils literal notranslate"><span class="pre">'-Infinity'</span></code>, <code class="docutils literal notranslate"><span class="pre">'Infinity'</span></code>, <code class="docutils literal notranslate"><span class="pre">'NaN'</span></code>. This can be used to raise an exception if invalid JSON numbers are encountered.</p> <p>If <em>strict</em> is false (<code class="docutils literal notranslate"><span class="pre">True</span></code> is the default), then control characters will be allowed inside strings. Control characters in this context are those with character codes in the 0–31 range, including <code class="docutils literal notranslate"><span class="pre">'\t'</span></code> (tab), <code class="docutils literal notranslate"><span class="pre">'\n'</span></code>, <code class="docutils literal notranslate"><span class="pre">'\r'</span></code> and <code class="docutils literal notranslate"><span class="pre">'\0'</span></code>.</p> <p>If the data being deserialized is not a valid JSON document, a <a class="reference internal" href="#json.JSONDecodeError" title="json.JSONDecodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">JSONDecodeError</span></code></a> will be raised.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>All parameters are now <a class="reference internal" href="../glossary.html#keyword-only-parameter"><span class="std std-ref">keyword-only</span></a>.</p> </div> <dl class="method"> <dt id="json.JSONDecoder.decode"> <code class="descname">decode</code><span class="sig-paren">(</span><em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONDecoder.decode" title="Permalink to this definition">¶</a></dt> <dd><p>Return the Python representation of <em>s</em> (a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> instance containing a JSON document).</p> <p><a class="reference internal" href="#json.JSONDecodeError" title="json.JSONDecodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">JSONDecodeError</span></code></a> will be raised if the given JSON document is not valid.</p> </dd></dl> <dl class="method"> <dt id="json.JSONDecoder.raw_decode"> <code class="descname">raw_decode</code><span class="sig-paren">(</span><em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONDecoder.raw_decode" title="Permalink to this definition">¶</a></dt> <dd><p>Decode a JSON document from <em>s</em> (a <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> beginning with a JSON document) and return a 2-tuple of the Python representation and the index in <em>s</em> where the document ended.</p> <p>This can be used to decode a JSON document from a string that may have extraneous data at the end.</p> </dd></dl> </dd></dl> <dl class="class"> <dt id="json.JSONEncoder"> <em class="property">class </em><code class="descclassname">json.</code><code class="descname">JSONEncoder</code><span class="sig-paren">(</span><em>*</em>, <em>skipkeys=False</em>, <em>ensure_ascii=True</em>, <em>check_circular=True</em>, <em>allow_nan=True</em>, <em>sort_keys=False</em>, <em>indent=None</em>, <em>separators=None</em>, <em>default=None</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONEncoder" title="Permalink to this definition">¶</a></dt> <dd><p>Extensible JSON encoder for Python data structures.</p> <p>Supports the following objects and types by default:</p> <table border="1" class="docutils" id="py-to-json-table"> <colgroup> <col width="73%" /> <col width="27%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Python</th> <th class="head">JSON</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td>dict</td> <td>object</td> </tr> <tr class="row-odd"><td>list, tuple</td> <td>array</td> </tr> <tr class="row-even"><td>str</td> <td>string</td> </tr> <tr class="row-odd"><td>int, float, int- &amp; float-derived Enums</td> <td>number</td> </tr> <tr class="row-even"><td>True</td> <td>true</td> </tr> <tr class="row-odd"><td>False</td> <td>false</td> </tr> <tr class="row-even"><td>None</td> <td>null</td> </tr> </tbody> </table> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.4: </span>Added support for int- and float-derived Enum classes.</p> </div> <p>To extend this to recognize other objects, subclass and implement a <a class="reference internal" href="#json.JSONEncoder.default" title="json.JSONEncoder.default"><code class="xref py py-meth docutils literal notranslate"><span class="pre">default()</span></code></a> method with another method that returns a serializable object for <code class="docutils literal notranslate"><span class="pre">o</span></code> if possible, otherwise it should call the superclass implementation (to raise <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>).</p> <p>If <em>skipkeys</em> is false (the default), then it is a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> to attempt encoding of keys that are not <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> or <code class="docutils literal notranslate"><span class="pre">None</span></code>. If <em>skipkeys</em> is true, such items are simply skipped.</p> <p>If <em>ensure_ascii</em> is true (the default), the output is guaranteed to have all incoming non-ASCII characters escaped. If <em>ensure_ascii</em> is false, these characters will be output as-is.</p> <p>If <em>check_circular</em> is true (the default), then lists, dicts, and custom encoded objects will be checked for circular references during encoding to prevent an infinite recursion (which would cause an <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a>). Otherwise, no such check takes place.</p> <p>If <em>allow_nan</em> is true (the default), then <code class="docutils literal notranslate"><span class="pre">NaN</span></code>, <code class="docutils literal notranslate"><span class="pre">Infinity</span></code>, and <code class="docutils literal notranslate"><span class="pre">-Infinity</span></code> will be encoded as such. This behavior is not JSON specification compliant, but is consistent with most JavaScript based encoders and decoders. Otherwise, it will be a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> to encode such floats.</p> <p>If <em>sort_keys</em> is true (default: <code class="docutils literal notranslate"><span class="pre">False</span></code>), then the output of dictionaries will be sorted by key; this is useful for regression tests to ensure that JSON serializations can be compared on a day-to-day basis.</p> <p>If <em>indent</em> is a non-negative integer or string, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0, negative, or <code class="docutils literal notranslate"><span class="pre">&quot;&quot;</span></code> will only insert newlines. <code class="docutils literal notranslate"><span class="pre">None</span></code> (the default) selects the most compact representation. Using a positive integer indent indents that many spaces per level. If <em>indent</em> is a string (such as <code class="docutils literal notranslate"><span class="pre">&quot;\t&quot;</span></code>), that string is used to indent each level.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span>Allow strings for <em>indent</em> in addition to integers.</p> </div> <p>If specified, <em>separators</em> should be an <code class="docutils literal notranslate"><span class="pre">(item_separator,</span> <span class="pre">key_separator)</span></code> tuple. The default is <code class="docutils literal notranslate"><span class="pre">(',</span> <span class="pre">',</span> <span class="pre">':</span> <span class="pre">')</span></code> if <em>indent</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code> and <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':</span> <span class="pre">')</span></code> otherwise. To get the most compact JSON representation, you should specify <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':')</span></code> to eliminate whitespace.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.4: </span>Use <code class="docutils literal notranslate"><span class="pre">(',',</span> <span class="pre">':</span> <span class="pre">')</span></code> as default if <em>indent</em> is not <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </div> <p>If specified, <em>default</em> should be a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>. If not specified, <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> is raised.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span>All parameters are now <a class="reference internal" href="../glossary.html#keyword-only-parameter"><span class="std std-ref">keyword-only</span></a>.</p> </div> <dl class="method"> <dt id="json.JSONEncoder.default"> <code class="descname">default</code><span class="sig-paren">(</span><em>o</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONEncoder.default" title="Permalink to this definition">¶</a></dt> <dd><p>Implement this method in a subclass such that it returns a serializable object for <em>o</em>, or calls the base implementation (to raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>).</p> <p>For example, to support arbitrary iterators, you could implement default like this:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">default</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">o</span><span class="p">):</span> <span class="k">try</span><span class="p">:</span> <span class="n">iterable</span> <span class="o">=</span> <span class="nb">iter</span><span class="p">(</span><span class="n">o</span><span class="p">)</span> <span class="k">except</span> <span class="ne">TypeError</span><span class="p">:</span> <span class="k">pass</span> <span class="k">else</span><span class="p">:</span> <span class="k">return</span> <span class="nb">list</span><span class="p">(</span><span class="n">iterable</span><span class="p">)</span> <span class="c1"># Let the base class default method raise the TypeError</span> <span class="k">return</span> <span class="n">json</span><span class="o">.</span><span class="n">JSONEncoder</span><span class="o">.</span><span class="n">default</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">o</span><span class="p">)</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="json.JSONEncoder.encode"> <code class="descname">encode</code><span class="sig-paren">(</span><em>o</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONEncoder.encode" title="Permalink to this definition">¶</a></dt> <dd><p>Return a JSON string representation of a Python data structure, <em>o</em>. For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">JSONEncoder</span><span class="p">()</span><span class="o">.</span><span class="n">encode</span><span class="p">({</span><span class="s2">&quot;foo&quot;</span><span class="p">:</span> <span class="p">[</span><span class="s2">&quot;bar&quot;</span><span class="p">,</span> <span class="s2">&quot;baz&quot;</span><span class="p">]})</span> <span class="go">&#39;{&quot;foo&quot;: [&quot;bar&quot;, &quot;baz&quot;]}&#39;</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="json.JSONEncoder.iterencode"> <code class="descname">iterencode</code><span class="sig-paren">(</span><em>o</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONEncoder.iterencode" title="Permalink to this definition">¶</a></dt> <dd><p>Encode the given object, <em>o</em>, and yield each string representation as available. For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">chunk</span> <span class="ow">in</span> <span class="n">json</span><span class="o">.</span><span class="n">JSONEncoder</span><span class="p">()</span><span class="o">.</span><span class="n">iterencode</span><span class="p">(</span><span class="n">bigobject</span><span class="p">):</span> <span class="n">mysocket</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">chunk</span><span class="p">)</span> </pre></div> </div> </dd></dl> </dd></dl> </div> <div class="section" id="exceptions"> <h2>19.2.3. Exceptions<a class="headerlink" href="#exceptions" title="Permalink to this headline">¶</a></h2> <dl class="exception"> <dt id="json.JSONDecodeError"> <em class="property">exception </em><code class="descclassname">json.</code><code class="descname">JSONDecodeError</code><span class="sig-paren">(</span><em>msg</em>, <em>doc</em>, <em>pos</em><span class="sig-paren">)</span><a class="headerlink" href="#json.JSONDecodeError" title="Permalink to this definition">¶</a></dt> <dd><p>Subclass of <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> with the following additional attributes:</p> <dl class="attribute"> <dt id="json.JSONDecodeError.msg"> <code class="descname">msg</code><a class="headerlink" href="#json.JSONDecodeError.msg" title="Permalink to this definition">¶</a></dt> <dd><p>The unformatted error message.</p> </dd></dl> <dl class="attribute"> <dt id="json.JSONDecodeError.doc"> <code class="descname">doc</code><a class="headerlink" href="#json.JSONDecodeError.doc" title="Permalink to this definition">¶</a></dt> <dd><p>The JSON document being parsed.</p> </dd></dl> <dl class="attribute"> <dt id="json.JSONDecodeError.pos"> <code class="descname">pos</code><a class="headerlink" href="#json.JSONDecodeError.pos" title="Permalink to this definition">¶</a></dt> <dd><p>The start index of <em>doc</em> where parsing failed.</p> </dd></dl> <dl class="attribute"> <dt id="json.JSONDecodeError.lineno"> <code class="descname">lineno</code><a class="headerlink" href="#json.JSONDecodeError.lineno" title="Permalink to this definition">¶</a></dt> <dd><p>The line corresponding to <em>pos</em>.</p> </dd></dl> <dl class="attribute"> <dt id="json.JSONDecodeError.colno"> <code class="descname">colno</code><a class="headerlink" href="#json.JSONDecodeError.colno" title="Permalink to this definition">¶</a></dt> <dd><p>The column corresponding to <em>pos</em>.</p> </dd></dl> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> </div> <div class="section" id="standard-compliance-and-interoperability"> <h2>19.2.4. Standard Compliance and Interoperability<a class="headerlink" href="#standard-compliance-and-interoperability" title="Permalink to this headline">¶</a></h2> <p>The JSON format is specified by <span class="target" id="index-2"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc7159.html"><strong>RFC 7159</strong></a> and by <a class="reference external" href="http://www.ecma-international.org/publications/standards/Ecma-404.htm">ECMA-404</a>. This section details this module’s level of compliance with the RFC. For simplicity, <a class="reference internal" href="#json.JSONEncoder" title="json.JSONEncoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONEncoder</span></code></a> and <a class="reference internal" href="#json.JSONDecoder" title="json.JSONDecoder"><code class="xref py py-class docutils literal notranslate"><span class="pre">JSONDecoder</span></code></a> subclasses, and parameters other than those explicitly mentioned, are not considered.</p> <p>This module does not comply with the RFC in a strict fashion, implementing some extensions that are valid JavaScript but not valid JSON. In particular:</p> <ul class="simple"> <li>Infinite and NaN number values are accepted and output;</li> <li>Repeated names within an object are accepted, and only the value of the last name-value pair is used.</li> </ul> <p>Since the RFC permits RFC-compliant parsers to accept input texts that are not RFC-compliant, this module’s deserializer is technically RFC-compliant under default settings.</p> <div class="section" id="character-encodings"> <h3>19.2.4.1. Character Encodings<a class="headerlink" href="#character-encodings" title="Permalink to this headline">¶</a></h3> <p>The RFC requires that JSON be represented using either UTF-8, UTF-16, or UTF-32, with UTF-8 being the recommended default for maximum interoperability.</p> <p>As permitted, though not required, by the RFC, this module’s serializer sets <em>ensure_ascii=True</em> by default, thus escaping the output so that the resulting strings only contain ASCII characters.</p> <p>Other than the <em>ensure_ascii</em> parameter, this module is defined strictly in terms of conversion between Python objects and <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">Unicode</span> <span class="pre">strings</span></code></a>, and thus does not otherwise directly address the issue of character encodings.</p> <p>The RFC prohibits adding a byte order mark (BOM) to the start of a JSON text, and this module’s serializer does not add a BOM to its output. The RFC permits, but does not require, JSON deserializers to ignore an initial BOM in their input. This module’s deserializer raises a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when an initial BOM is present.</p> <p>The RFC does not explicitly forbid JSON strings which contain byte sequences that don’t correspond to valid Unicode characters (e.g. unpaired UTF-16 surrogates), but it does note that they may cause interoperability problems. By default, this module accepts and outputs (when present in the original <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>) code points for such sequences.</p> </div> <div class="section" id="infinite-and-nan-number-values"> <h3>19.2.4.2. Infinite and NaN Number Values<a class="headerlink" href="#infinite-and-nan-number-values" title="Permalink to this headline">¶</a></h3> <p>The RFC does not permit the representation of infinite or NaN number values. Despite that, by default, this module accepts and outputs <code class="docutils literal notranslate"><span class="pre">Infinity</span></code>, <code class="docutils literal notranslate"><span class="pre">-Infinity</span></code>, and <code class="docutils literal notranslate"><span class="pre">NaN</span></code> as if they were valid JSON number literal values:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="c1"># Neither of these calls raises an exception, but the results are not valid JSON</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="nb">float</span><span class="p">(</span><span class="s1">&#39;-inf&#39;</span><span class="p">))</span> <span class="go">&#39;-Infinity&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="nb">float</span><span class="p">(</span><span class="s1">&#39;nan&#39;</span><span class="p">))</span> <span class="go">&#39;NaN&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="c1"># Same when deserializing</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;-Infinity&#39;</span><span class="p">)</span> <span class="go">-inf</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="s1">&#39;NaN&#39;</span><span class="p">)</span> <span class="go">nan</span> </pre></div> </div> <p>In the serializer, the <em>allow_nan</em> parameter can be used to alter this behavior. In the deserializer, the <em>parse_constant</em> parameter can be used to alter this behavior.</p> </div> <div class="section" id="repeated-names-within-an-object"> <h3>19.2.4.3. Repeated Names Within an Object<a class="headerlink" href="#repeated-names-within-an-object" title="Permalink to this headline">¶</a></h3> <p>The RFC specifies that the names within a JSON object should be unique, but does not mandate how repeated names in JSON objects should be handled. By default, this module does not raise an exception; instead, it ignores all but the last name-value pair for a given name:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">weird_json</span> <span class="o">=</span> <span class="s1">&#39;{&quot;x&quot;: 1, &quot;x&quot;: 2, &quot;x&quot;: 3}&#39;</span> <span class="gp">&gt;&gt;&gt; </span><span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">weird_json</span><span class="p">)</span> <span class="go">{&#39;x&#39;: 3}</span> </pre></div> </div> <p>The <em>object_pairs_hook</em> parameter can be used to alter this behavior.</p> </div> <div class="section" id="top-level-non-object-non-array-values"> <h3>19.2.4.4. Top-level Non-Object, Non-Array Values<a class="headerlink" href="#top-level-non-object-non-array-values" title="Permalink to this headline">¶</a></h3> <p>The old version of JSON specified by the obsolete <span class="target" id="index-3"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc4627.html"><strong>RFC 4627</strong></a> required that the top-level value of a JSON text must be either a JSON object or array (Python <a class="reference internal" href="stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> or <a class="reference internal" href="stdtypes.html#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a>), and could not be a JSON null, boolean, number, or string value. <span class="target" id="index-4"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc7159.html"><strong>RFC 7159</strong></a> removed that restriction, and this module does not and has never implemented that restriction in either its serializer or its deserializer.</p> <p>Regardless, for maximum interoperability, you may wish to voluntarily adhere to the restriction yourself.</p> </div> <div class="section" id="implementation-limitations"> <h3>19.2.4.5. Implementation Limitations<a class="headerlink" href="#implementation-limitations" title="Permalink to this headline">¶</a></h3> <p>Some JSON deserializer implementations may set limits on:</p> <ul class="simple"> <li>the size of accepted JSON texts</li> <li>the maximum level of nesting of JSON objects and arrays</li> <li>the range and precision of JSON numbers</li> <li>the content and maximum length of JSON strings</li> </ul> <p>This module does not impose any such limits beyond those of the relevant Python datatypes themselves or the Python interpreter itself.</p> <p>When serializing to JSON, beware any such limitations in applications that may consume your JSON. In particular, it is common for JSON numbers to be deserialized into IEEE 754 double precision numbers and thus subject to that representation’s range and precision limitations. This is especially relevant when serializing Python <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> values of extremely large magnitude, or when serializing instances of “exotic” numerical types such as <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>.</p> </div> </div> <div class="section" id="module-json.tool"> <span id="command-line-interface"></span><span id="json-commandline"></span><h2>19.2.5. Command Line Interface<a class="headerlink" href="#module-json.tool" title="Permalink to this headline">¶</a></h2> <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.6/Lib/json/tool.py">Lib/json/tool.py</a></p> <hr class="docutils" /> <p>The <a class="reference internal" href="#module-json.tool" title="json.tool: A command line to validate and pretty-print JSON."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json.tool</span></code></a> module provides a simple command line interface to validate and pretty-print JSON objects.</p> <p>If the optional <code class="docutils literal notranslate"><span class="pre">infile</span></code> and <code class="docutils literal notranslate"><span class="pre">outfile</span></code> arguments are not specified, <a class="reference internal" href="sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.stdin</span></code></a> and <a class="reference internal" href="sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.stdout</span></code></a> will be used respectively:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> <span class="nb">echo</span> <span class="s1">&#39;{&quot;json&quot;: &quot;obj&quot;}&#39;</span> <span class="p">|</span> python -m json.tool <span class="go">{</span> <span class="go"> &quot;json&quot;: &quot;obj&quot;</span> <span class="go">}</span> <span class="gp">$</span> <span class="nb">echo</span> <span class="s1">&#39;{1.2:3.4}&#39;</span> <span class="p">|</span> python -m json.tool <span class="go">Expecting property name enclosed in double quotes: line 1 column 2 (char 1)</span> </pre></div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span>The output is now in the same order as the input. Use the <a class="reference internal" href="#cmdoption-sort-keys"><code class="xref std std-option docutils literal notranslate"><span class="pre">--sort-keys</span></code></a> option to sort the output of dictionaries alphabetically by key.</p> </div> <div class="section" id="command-line-options"> <h3>19.2.5.1. Command line options<a class="headerlink" href="#command-line-options" title="Permalink to this headline">¶</a></h3> <dl class="cmdoption"> <dt id="cmdoption-arg-infile"> <code class="descname">infile</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-arg-infile" title="Permalink to this definition">¶</a></dt> <dd><p>The JSON file to be validated or pretty-printed:</p> <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python -m json.tool mp_films.json <span class="go">[</span> <span class="go"> {</span> <span class="go"> &quot;title&quot;: &quot;And Now for Something Completely Different&quot;,</span> <span class="go"> &quot;year&quot;: 1971</span> <span class="go"> },</span> <span class="go"> {</span> <span class="go"> &quot;title&quot;: &quot;Monty Python and the Holy Grail&quot;,</span> <span class="go"> &quot;year&quot;: 1975</span> <span class="go"> }</span> <span class="go">]</span> </pre></div> </div> <p>If <em>infile</em> is not specified, read from <a class="reference internal" href="sys.html#sys.stdin" title="sys.stdin"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.stdin</span></code></a>.</p> </dd></dl> <dl class="cmdoption"> <dt id="cmdoption-arg-outfile"> <code class="descname">outfile</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-arg-outfile" title="Permalink to this definition">¶</a></dt> <dd><p>Write the output of the <em>infile</em> to the given <em>outfile</em>. Otherwise, write it to <a class="reference internal" href="sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-attr docutils literal notranslate"><span class="pre">sys.stdout</span></code></a>.</p> </dd></dl> <dl class="cmdoption"> <dt id="cmdoption-sort-keys"> <code class="descname">--sort-keys</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-sort-keys" title="Permalink to this definition">¶</a></dt> <dd><p>Sort the output of dictionaries alphabetically by key.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> <dl class="cmdoption"> <dt id="cmdoption-h"> <code class="descname">-h</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--help</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-h" title="Permalink to this definition">¶</a></dt> <dd><p>Show the help message.</p> </dd></dl> <p class="rubric">Footnotes</p> <table class="docutils footnote" frame="void" id="rfc-errata" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>As noted in <a class="reference external" href="https://www.rfc-editor.org/errata_search.php?rfc=7159">the errata for RFC 7159</a>, JSON permits literal U+2028 (LINE SEPARATOR) and U+2029 (PARAGRAPH SEPARATOR) characters in strings, whereas JavaScript (as of ECMAScript Edition 5.1) does not.</td></tr> </tbody> </table> </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="#">19.2. <code class="docutils literal notranslate"><span class="pre">json</span></code> — JSON encoder and decoder</a><ul> <li><a class="reference internal" href="#basic-usage">19.2.1. Basic Usage</a></li> <li><a class="reference internal" href="#encoders-and-decoders">19.2.2. Encoders and Decoders</a></li> <li><a class="reference internal" href="#exceptions">19.2.3. Exceptions</a></li> <li><a class="reference internal" href="#standard-compliance-and-interoperability">19.2.4. Standard Compliance and Interoperability</a><ul> <li><a class="reference internal" href="#character-encodings">19.2.4.1. Character Encodings</a></li> <li><a class="reference internal" href="#infinite-and-nan-number-values">19.2.4.2. Infinite and NaN Number Values</a></li> <li><a class="reference internal" href="#repeated-names-within-an-object">19.2.4.3. Repeated Names Within an Object</a></li> <li><a class="reference internal" href="#top-level-non-object-non-array-values">19.2.4.4. Top-level Non-Object, Non-Array Values</a></li> <li><a class="reference internal" href="#implementation-limitations">19.2.4.5. Implementation Limitations</a></li> </ul> </li> <li><a class="reference internal" href="#module-json.tool">19.2.5. Command Line Interface</a><ul> <li><a class="reference internal" href="#command-line-options">19.2.5.1. Command line options</a></li> </ul> </li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="email.iterators.html" title="previous chapter">19.1.15. <code class="docutils literal notranslate"><span class="pre">email.iterators</span></code>: Iterators</a></p> <h4>Next topic</h4> <p class="topless"><a href="mailcap.html" title="next chapter">19.3. <code class="docutils literal notranslate"><span class="pre">mailcap</span></code> — Mailcap file handling</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/3.6/Doc/library/json.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> </div> <div class="clearer"></div> </div> <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" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="mailcap.html" title="19.3. mailcap — Mailcap file handling" >next</a> |</li> <li class="right" > <a href="email.iterators.html" title="19.1.15. email.iterators: Iterators" >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> &#187;</li> <li> <a href="../index.html">3.6.7 Documentation</a> &#187; </li> <li class="nav-item nav-item-1"><a href="index.html" >The Python Standard Library</a> &#187;</li> <li class="nav-item nav-item-2"><a href="netdata.html" >19. 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