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  <h1>Source code for django.db.models.aggregates</h1><div class="highlight"><pre>
<span></span><span class="sd">&quot;&quot;&quot;</span>
<span class="sd">Classes to represent the definitions of aggregate functions.</span>
<span class="sd">&quot;&quot;&quot;</span>
<span class="kn">from</span> <span class="nn">django.core.exceptions</span> <span class="k">import</span> <span class="n">FieldError</span>
<span class="kn">from</span> <span class="nn">django.db.models.expressions</span> <span class="k">import</span> <span class="n">Func</span><span class="p">,</span> <span class="n">Star</span>
<span class="kn">from</span> <span class="nn">django.db.models.fields</span> <span class="k">import</span> <span class="n">FloatField</span><span class="p">,</span> <span class="n">IntegerField</span>

<span class="n">__all__</span> <span class="o">=</span> <span class="p">[</span>
    <span class="s1">&#39;Aggregate&#39;</span><span class="p">,</span> <span class="s1">&#39;Avg&#39;</span><span class="p">,</span> <span class="s1">&#39;Count&#39;</span><span class="p">,</span> <span class="s1">&#39;Max&#39;</span><span class="p">,</span> <span class="s1">&#39;Min&#39;</span><span class="p">,</span> <span class="s1">&#39;StdDev&#39;</span><span class="p">,</span> <span class="s1">&#39;Sum&#39;</span><span class="p">,</span> <span class="s1">&#39;Variance&#39;</span><span class="p">,</span>
<span class="p">]</span>


<div class="viewcode-block" id="Aggregate"><a class="viewcode-back" href="../../../../ref/models/expressions.html#django.db.models.Aggregate">[docs]</a><span class="k">class</span> <span class="nc">Aggregate</span><span class="p">(</span><span class="n">Func</span><span class="p">):</span>
    <span class="n">contains_aggregate</span> <span class="o">=</span> <span class="kc">True</span>
    <span class="n">name</span> <span class="o">=</span> <span class="kc">None</span>

    <span class="k">def</span> <span class="nf">resolve_expression</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">query</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">allow_joins</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span> <span class="n">reuse</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">summarize</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="n">for_save</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
        <span class="k">assert</span> <span class="nb">len</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span>
        <span class="c1"># Aggregates are not allowed in UPDATE queries, so ignore for_save</span>
        <span class="n">c</span> <span class="o">=</span> <span class="nb">super</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">resolve_expression</span><span class="p">(</span><span class="n">query</span><span class="p">,</span> <span class="n">allow_joins</span><span class="p">,</span> <span class="n">reuse</span><span class="p">,</span> <span class="n">summarize</span><span class="p">)</span>
        <span class="k">if</span> <span class="n">c</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">contains_aggregate</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">summarize</span><span class="p">:</span>
            <span class="n">name</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">name</span>
            <span class="k">raise</span> <span class="n">FieldError</span><span class="p">(</span><span class="s2">&quot;Cannot compute </span><span class="si">%s</span><span class="s2">(&#39;</span><span class="si">%s</span><span class="s2">&#39;): &#39;</span><span class="si">%s</span><span class="s2">&#39; is an aggregate&quot;</span> <span class="o">%</span> <span class="p">(</span>
                <span class="n">c</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">name</span><span class="p">,</span> <span class="n">name</span><span class="p">))</span>
        <span class="n">c</span><span class="o">.</span><span class="n">_patch_aggregate</span><span class="p">(</span><span class="n">query</span><span class="p">)</span>  <span class="c1"># backward-compatibility support</span>
        <span class="k">return</span> <span class="n">c</span>

    <span class="nd">@property</span>
    <span class="k">def</span> <span class="nf">input_field</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>

    <span class="nd">@property</span>
    <span class="k">def</span> <span class="nf">default_alias</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="s1">&#39;name&#39;</span><span class="p">):</span>
            <span class="k">return</span> <span class="s1">&#39;</span><span class="si">%s</span><span class="s1">__</span><span class="si">%s</span><span class="s1">&#39;</span> <span class="o">%</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">name</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">lower</span><span class="p">())</span>
        <span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="s2">&quot;Complex expressions require an alias&quot;</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">get_group_by_cols</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="k">return</span> <span class="p">[]</span>

    <span class="k">def</span> <span class="nf">_patch_aggregate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">query</span><span class="p">):</span>
        <span class="sd">&quot;&quot;&quot;</span>
<span class="sd">        Helper method for patching 3rd party aggregates that do not yet support</span>
<span class="sd">        the new way of subclassing. This method will be removed in Django 1.10.</span>

<span class="sd">        add_to_query(query, alias, col, source, is_summary) will be defined on</span>
<span class="sd">        legacy aggregates which, in turn, instantiates the SQL implementation of</span>
<span class="sd">        the aggregate. In all the cases found, the general implementation of</span>
<span class="sd">        add_to_query looks like:</span>

<span class="sd">        def add_to_query(self, query, alias, col, source, is_summary):</span>
<span class="sd">            klass = SQLImplementationAggregate</span>
<span class="sd">            aggregate = klass(col, source=source, is_summary=is_summary, **self.extra)</span>
<span class="sd">            query.aggregates[alias] = aggregate</span>

<span class="sd">        By supplying a known alias, we can get the SQLAggregate out of the</span>
<span class="sd">        aggregates dict, and use the sql_function and sql_template attributes</span>
<span class="sd">        to patch *this* aggregate.</span>
<span class="sd">        &quot;&quot;&quot;</span>
        <span class="k">if</span> <span class="ow">not</span> <span class="nb">hasattr</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="s1">&#39;add_to_query&#39;</span><span class="p">)</span> <span class="ow">or</span> <span class="bp">self</span><span class="o">.</span><span class="n">function</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span>

        <span class="n">placeholder_alias</span> <span class="o">=</span> <span class="s2">&quot;_XXXXXXXX_&quot;</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">add_to_query</span><span class="p">(</span><span class="n">query</span><span class="p">,</span> <span class="n">placeholder_alias</span><span class="p">,</span> <span class="kc">None</span><span class="p">,</span> <span class="kc">None</span><span class="p">,</span> <span class="kc">None</span><span class="p">)</span>
        <span class="n">sql_aggregate</span> <span class="o">=</span> <span class="n">query</span><span class="o">.</span><span class="n">aggregates</span><span class="o">.</span><span class="n">pop</span><span class="p">(</span><span class="n">placeholder_alias</span><span class="p">)</span>
        <span class="k">if</span> <span class="s1">&#39;sql_function&#39;</span> <span class="ow">not</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">extra</span> <span class="ow">and</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">sql_aggregate</span><span class="p">,</span> <span class="s1">&#39;sql_function&#39;</span><span class="p">):</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">extra</span><span class="p">[</span><span class="s1">&#39;function&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="n">sql_aggregate</span><span class="o">.</span><span class="n">sql_function</span>

        <span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">sql_aggregate</span><span class="p">,</span> <span class="s1">&#39;sql_template&#39;</span><span class="p">):</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">extra</span><span class="p">[</span><span class="s1">&#39;template&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="n">sql_aggregate</span><span class="o">.</span><span class="n">sql_template</span></div>


<div class="viewcode-block" id="Avg"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Avg">[docs]</a><span class="k">class</span> <span class="nc">Avg</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;AVG&#39;</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Avg&#39;</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">expression</span><span class="p">,</span> <span class="o">**</span><span class="n">extra</span><span class="p">):</span>
        <span class="nb">super</span><span class="p">(</span><span class="n">Avg</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="n">expression</span><span class="p">,</span> <span class="n">output_field</span><span class="o">=</span><span class="n">FloatField</span><span class="p">(),</span> <span class="o">**</span><span class="n">extra</span><span class="p">)</span>

    <span class="k">def</span> <span class="nf">convert_value</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">expression</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">value</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span> <span class="n">value</span>
        <span class="k">return</span> <span class="nb">float</span><span class="p">(</span><span class="n">value</span><span class="p">)</span></div>


<div class="viewcode-block" id="Count"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Count">[docs]</a><span class="k">class</span> <span class="nc">Count</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;COUNT&#39;</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Count&#39;</span>
    <span class="n">template</span> <span class="o">=</span> <span class="s1">&#39;</span><span class="si">%(function)s</span><span class="s1">(</span><span class="si">%(distinct)s%(expressions)s</span><span class="s1">)&#39;</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">expression</span><span class="p">,</span> <span class="n">distinct</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="o">**</span><span class="n">extra</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">expression</span> <span class="o">==</span> <span class="s1">&#39;*&#39;</span><span class="p">:</span>
            <span class="n">expression</span> <span class="o">=</span> <span class="n">Star</span><span class="p">()</span>
        <span class="nb">super</span><span class="p">(</span><span class="n">Count</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span>
            <span class="n">expression</span><span class="p">,</span> <span class="n">distinct</span><span class="o">=</span><span class="s1">&#39;DISTINCT &#39;</span> <span class="k">if</span> <span class="n">distinct</span> <span class="k">else</span> <span class="s1">&#39;&#39;</span><span class="p">,</span> <span class="n">output_field</span><span class="o">=</span><span class="n">IntegerField</span><span class="p">(),</span> <span class="o">**</span><span class="n">extra</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="s2">&quot;</span><span class="si">{}</span><span class="s2">(</span><span class="si">{}</span><span class="s2">, distinct=</span><span class="si">{}</span><span class="s2">)&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">arg_joiner</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span> <span class="k">for</span> <span class="n">arg</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">),</span>
            <span class="s1">&#39;False&#39;</span> <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">extra</span><span class="p">[</span><span class="s1">&#39;distinct&#39;</span><span class="p">]</span> <span class="o">==</span> <span class="s1">&#39;&#39;</span> <span class="k">else</span> <span class="s1">&#39;True&#39;</span><span class="p">,</span>
        <span class="p">)</span>

    <span class="k">def</span> <span class="nf">convert_value</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">expression</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">value</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span> <span class="mi">0</span>
        <span class="k">return</span> <span class="nb">int</span><span class="p">(</span><span class="n">value</span><span class="p">)</span></div>


<div class="viewcode-block" id="Max"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Max">[docs]</a><span class="k">class</span> <span class="nc">Max</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;MAX&#39;</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Max&#39;</span></div>


<div class="viewcode-block" id="Min"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Min">[docs]</a><span class="k">class</span> <span class="nc">Min</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;MIN&#39;</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Min&#39;</span></div>


<div class="viewcode-block" id="StdDev"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.StdDev">[docs]</a><span class="k">class</span> <span class="nc">StdDev</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;StdDev&#39;</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">expression</span><span class="p">,</span> <span class="n">sample</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="o">**</span><span class="n">extra</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;STDDEV_SAMP&#39;</span> <span class="k">if</span> <span class="n">sample</span> <span class="k">else</span> <span class="s1">&#39;STDDEV_POP&#39;</span>
        <span class="nb">super</span><span class="p">(</span><span class="n">StdDev</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="n">expression</span><span class="p">,</span> <span class="n">output_field</span><span class="o">=</span><span class="n">FloatField</span><span class="p">(),</span> <span class="o">**</span><span class="n">extra</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="s2">&quot;</span><span class="si">{}</span><span class="s2">(</span><span class="si">{}</span><span class="s2">, sample=</span><span class="si">{}</span><span class="s2">)&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">arg_joiner</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span> <span class="k">for</span> <span class="n">arg</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">),</span>
            <span class="s1">&#39;False&#39;</span> <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">function</span> <span class="o">==</span> <span class="s1">&#39;STDDEV_POP&#39;</span> <span class="k">else</span> <span class="s1">&#39;True&#39;</span><span class="p">,</span>
        <span class="p">)</span>

    <span class="k">def</span> <span class="nf">convert_value</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">expression</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">value</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span> <span class="n">value</span>
        <span class="k">return</span> <span class="nb">float</span><span class="p">(</span><span class="n">value</span><span class="p">)</span></div>


<div class="viewcode-block" id="Sum"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Sum">[docs]</a><span class="k">class</span> <span class="nc">Sum</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;SUM&#39;</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Sum&#39;</span></div>


<div class="viewcode-block" id="Variance"><a class="viewcode-back" href="../../../../ref/models/querysets.html#django.db.models.Variance">[docs]</a><span class="k">class</span> <span class="nc">Variance</span><span class="p">(</span><span class="n">Aggregate</span><span class="p">):</span>
    <span class="n">name</span> <span class="o">=</span> <span class="s1">&#39;Variance&#39;</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">expression</span><span class="p">,</span> <span class="n">sample</span><span class="o">=</span><span class="kc">False</span><span class="p">,</span> <span class="o">**</span><span class="n">extra</span><span class="p">):</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">function</span> <span class="o">=</span> <span class="s1">&#39;VAR_SAMP&#39;</span> <span class="k">if</span> <span class="n">sample</span> <span class="k">else</span> <span class="s1">&#39;VAR_POP&#39;</span>
        <span class="nb">super</span><span class="p">(</span><span class="n">Variance</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="n">expression</span><span class="p">,</span> <span class="n">output_field</span><span class="o">=</span><span class="n">FloatField</span><span class="p">(),</span> <span class="o">**</span><span class="n">extra</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="s2">&quot;</span><span class="si">{}</span><span class="s2">(</span><span class="si">{}</span><span class="s2">, sample=</span><span class="si">{}</span><span class="s2">)&quot;</span><span class="o">.</span><span class="n">format</span><span class="p">(</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span><span class="p">,</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">arg_joiner</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span> <span class="k">for</span> <span class="n">arg</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">source_expressions</span><span class="p">),</span>
            <span class="s1">&#39;False&#39;</span> <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">function</span> <span class="o">==</span> <span class="s1">&#39;VAR_POP&#39;</span> <span class="k">else</span> <span class="s1">&#39;True&#39;</span><span class="p">,</span>
        <span class="p">)</span>

    <span class="k">def</span> <span class="nf">convert_value</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">expression</span><span class="p">,</span> <span class="n">connection</span><span class="p">,</span> <span class="n">context</span><span class="p">):</span>
        <span class="k">if</span> <span class="n">value</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span> <span class="n">value</span>
        <span class="k">return</span> <span class="nb">float</span><span class="p">(</span><span class="n">value</span><span class="p">)</span></div>
</pre></div>

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