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Functional Programming Modules</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-operator"> <span id="operator-standard-operators-as-functions"></span><h1>10.3. <a class="reference internal" href="#module-operator" title="operator: Functions corresponding to the standard operators."><tt class="xref py py-mod docutils literal"><span class="pre">operator</span></tt></a> — Standard operators as functions<a class="headerlink" href="#module-operator" title="Permalink to this headline">¶</a></h1> <p>The <a class="reference internal" href="#module-operator" title="operator: Functions corresponding to the standard operators."><tt class="xref py py-mod docutils literal"><span class="pre">operator</span></tt></a> module exports a set of efficient functions corresponding to the intrinsic operators of Python. For example, <tt class="docutils literal"><span class="pre">operator.add(x,</span> <span class="pre">y)</span></tt> is equivalent to the expression <tt class="docutils literal"><span class="pre">x+y</span></tt>. The function names are those used for special class methods; variants without leading and trailing <tt class="docutils literal"><span class="pre">__</span></tt> are also provided for convenience.</p> <p>The functions fall into categories that perform object comparisons, logical operations, mathematical operations and sequence operations.</p> <p>The object comparison functions are useful for all objects, and are named after the rich comparison operators they support:</p> <dl class="function"> <dt id="operator.lt"> <tt class="descclassname">operator.</tt><tt class="descname">lt</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.lt" title="Permalink to this definition">¶</a></dt> <dt id="operator.le"> <tt class="descclassname">operator.</tt><tt class="descname">le</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.le" title="Permalink to this definition">¶</a></dt> <dt id="operator.eq"> <tt class="descclassname">operator.</tt><tt class="descname">eq</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.eq" title="Permalink to this definition">¶</a></dt> <dt id="operator.ne"> <tt class="descclassname">operator.</tt><tt class="descname">ne</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ne" title="Permalink to this definition">¶</a></dt> <dt id="operator.ge"> <tt class="descclassname">operator.</tt><tt class="descname">ge</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ge" title="Permalink to this definition">¶</a></dt> <dt id="operator.gt"> <tt class="descclassname">operator.</tt><tt class="descname">gt</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.gt" title="Permalink to this definition">¶</a></dt> <dt id="operator.__lt__"> <tt class="descclassname">operator.</tt><tt class="descname">__lt__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__lt__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__le__"> <tt class="descclassname">operator.</tt><tt class="descname">__le__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__le__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__eq__"> <tt class="descclassname">operator.</tt><tt class="descname">__eq__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__eq__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ne__"> <tt class="descclassname">operator.</tt><tt class="descname">__ne__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ne__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ge__"> <tt class="descclassname">operator.</tt><tt class="descname">__ge__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ge__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__gt__"> <tt class="descclassname">operator.</tt><tt class="descname">__gt__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__gt__" title="Permalink to this definition">¶</a></dt> <dd><p>Perform “rich comparisons” between <em>a</em> and <em>b</em>. Specifically, <tt class="docutils literal"><span class="pre">lt(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre"><</span> <span class="pre">b</span></tt>, <tt class="docutils literal"><span class="pre">le(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre"><=</span> <span class="pre">b</span></tt>, <tt class="docutils literal"><span class="pre">eq(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></tt>, <tt class="docutils literal"><span class="pre">ne(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">!=</span> <span class="pre">b</span></tt>, <tt class="docutils literal"><span class="pre">gt(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">></span> <span class="pre">b</span></tt> and <tt class="docutils literal"><span class="pre">ge(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">>=</span> <span class="pre">b</span></tt>. Note that these functions can return any value, which may or may not be interpretable as a Boolean value. See <a class="reference internal" href="../reference/expressions.html#comparisons"><em>Comparisons</em></a> for more information about rich comparisons.</p> </dd></dl> <p>The logical operations are also generally applicable to all objects, and support truth tests, identity tests, and boolean operations:</p> <dl class="function"> <dt id="operator.not_"> <tt class="descclassname">operator.</tt><tt class="descname">not_</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.not_" title="Permalink to this definition">¶</a></dt> <dt id="operator.__not__"> <tt class="descclassname">operator.</tt><tt class="descname">__not__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__not__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the outcome of <a class="reference internal" href="../reference/expressions.html#not"><tt class="xref std std-keyword docutils literal"><span class="pre">not</span></tt></a> <em>obj</em>. (Note that there is no <a class="reference internal" href="#operator.__not__" title="operator.__not__"><tt class="xref py py-meth docutils literal"><span class="pre">__not__()</span></tt></a> method for object instances; only the interpreter core defines this operation. The result is affected by the <a class="reference internal" href="../reference/datamodel.html#object.__bool__" title="object.__bool__"><tt class="xref py py-meth docutils literal"><span class="pre">__bool__()</span></tt></a> and <a class="reference internal" href="../reference/datamodel.html#object.__len__" title="object.__len__"><tt class="xref py py-meth docutils literal"><span class="pre">__len__()</span></tt></a> methods.)</p> </dd></dl> <dl class="function"> <dt id="operator.truth"> <tt class="descclassname">operator.</tt><tt class="descname">truth</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.truth" title="Permalink to this definition">¶</a></dt> <dd><p>Return <a class="reference internal" href="constants.html#True" title="True"><tt class="xref py py-const xref docutils literal"><span class="pre">True</span></tt></a> if <em>obj</em> is true, and <a class="reference internal" href="constants.html#False" title="False"><tt class="xref py py-const xref docutils literal"><span class="pre">False</span></tt></a> otherwise. This is equivalent to using the <a class="reference internal" href="functions.html#bool" title="bool"><tt class="xref py py-class docutils literal"><span class="pre">bool</span></tt></a> constructor.</p> </dd></dl> <dl class="function"> <dt id="operator.is_"> <tt class="descclassname">operator.</tt><tt class="descname">is_</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.is_" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">is</span> <span class="pre">b</span></tt>. Tests object identity.</p> </dd></dl> <dl class="function"> <dt id="operator.is_not"> <tt class="descclassname">operator.</tt><tt class="descname">is_not</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.is_not" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">is</span> <span class="pre">not</span> <span class="pre">b</span></tt>. Tests object identity.</p> </dd></dl> <p>The mathematical and bitwise operations are the most numerous:</p> <dl class="function"> <dt id="operator.abs"> <tt class="descclassname">operator.</tt><tt class="descname">abs</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.abs" title="Permalink to this definition">¶</a></dt> <dt id="operator.__abs__"> <tt class="descclassname">operator.</tt><tt class="descname">__abs__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__abs__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the absolute value of <em>obj</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.add"> <tt class="descclassname">operator.</tt><tt class="descname">add</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.add" title="Permalink to this definition">¶</a></dt> <dt id="operator.__add__"> <tt class="descclassname">operator.</tt><tt class="descname">__add__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__add__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">+</span> <span class="pre">b</span></tt>, for <em>a</em> and <em>b</em> numbers.</p> </dd></dl> <dl class="function"> <dt id="operator.and_"> <tt class="descclassname">operator.</tt><tt class="descname">and_</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.and_" title="Permalink to this definition">¶</a></dt> <dt id="operator.__and__"> <tt class="descclassname">operator.</tt><tt class="descname">__and__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__and__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the bitwise and of <em>a</em> and <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.floordiv"> <tt class="descclassname">operator.</tt><tt class="descname">floordiv</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.floordiv" title="Permalink to this definition">¶</a></dt> <dt id="operator.__floordiv__"> <tt class="descclassname">operator.</tt><tt class="descname">__floordiv__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__floordiv__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">//</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.index"> <tt class="descclassname">operator.</tt><tt class="descname">index</tt><big>(</big><em>a</em><big>)</big><a class="headerlink" href="#operator.index" title="Permalink to this definition">¶</a></dt> <dt id="operator.__index__"> <tt class="descclassname">operator.</tt><tt class="descname">__index__</tt><big>(</big><em>a</em><big>)</big><a class="headerlink" href="#operator.__index__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <em>a</em> converted to an integer. Equivalent to <tt class="docutils literal"><span class="pre">a.__index__()</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.inv"> <tt class="descclassname">operator.</tt><tt class="descname">inv</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.inv" title="Permalink to this definition">¶</a></dt> <dt id="operator.invert"> <tt class="descclassname">operator.</tt><tt class="descname">invert</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.invert" title="Permalink to this definition">¶</a></dt> <dt id="operator.__inv__"> <tt class="descclassname">operator.</tt><tt class="descname">__inv__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__inv__" title="Permalink to this definition">¶</a></dt> <dt id="operator.__invert__"> <tt class="descclassname">operator.</tt><tt class="descname">__invert__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__invert__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the bitwise inverse of the number <em>obj</em>. This is equivalent to <tt class="docutils literal"><span class="pre">~obj</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.lshift"> <tt class="descclassname">operator.</tt><tt class="descname">lshift</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.lshift" title="Permalink to this definition">¶</a></dt> <dt id="operator.__lshift__"> <tt class="descclassname">operator.</tt><tt class="descname">__lshift__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__lshift__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <em>a</em> shifted left by <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.mod"> <tt class="descclassname">operator.</tt><tt class="descname">mod</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.mod" title="Permalink to this definition">¶</a></dt> <dt id="operator.__mod__"> <tt class="descclassname">operator.</tt><tt class="descname">__mod__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__mod__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">%</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.mul"> <tt class="descclassname">operator.</tt><tt class="descname">mul</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.mul" title="Permalink to this definition">¶</a></dt> <dt id="operator.__mul__"> <tt class="descclassname">operator.</tt><tt class="descname">__mul__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__mul__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">*</span> <span class="pre">b</span></tt>, for <em>a</em> and <em>b</em> numbers.</p> </dd></dl> <dl class="function"> <dt id="operator.neg"> <tt class="descclassname">operator.</tt><tt class="descname">neg</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.neg" title="Permalink to this definition">¶</a></dt> <dt id="operator.__neg__"> <tt class="descclassname">operator.</tt><tt class="descname">__neg__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__neg__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <em>obj</em> negated (<tt class="docutils literal"><span class="pre">-obj</span></tt>).</p> </dd></dl> <dl class="function"> <dt id="operator.or_"> <tt class="descclassname">operator.</tt><tt class="descname">or_</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.or_" title="Permalink to this definition">¶</a></dt> <dt id="operator.__or__"> <tt class="descclassname">operator.</tt><tt class="descname">__or__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__or__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the bitwise or of <em>a</em> and <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.pos"> <tt class="descclassname">operator.</tt><tt class="descname">pos</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.pos" title="Permalink to this definition">¶</a></dt> <dt id="operator.__pos__"> <tt class="descclassname">operator.</tt><tt class="descname">__pos__</tt><big>(</big><em>obj</em><big>)</big><a class="headerlink" href="#operator.__pos__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <em>obj</em> positive (<tt class="docutils literal"><span class="pre">+obj</span></tt>).</p> </dd></dl> <dl class="function"> <dt id="operator.pow"> <tt class="descclassname">operator.</tt><tt class="descname">pow</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.pow" title="Permalink to this definition">¶</a></dt> <dt id="operator.__pow__"> <tt class="descclassname">operator.</tt><tt class="descname">__pow__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__pow__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">**</span> <span class="pre">b</span></tt>, for <em>a</em> and <em>b</em> numbers.</p> </dd></dl> <dl class="function"> <dt id="operator.rshift"> <tt class="descclassname">operator.</tt><tt class="descname">rshift</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.rshift" title="Permalink to this definition">¶</a></dt> <dt id="operator.__rshift__"> <tt class="descclassname">operator.</tt><tt class="descname">__rshift__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__rshift__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <em>a</em> shifted right by <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.sub"> <tt class="descclassname">operator.</tt><tt class="descname">sub</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.sub" title="Permalink to this definition">¶</a></dt> <dt id="operator.__sub__"> <tt class="descclassname">operator.</tt><tt class="descname">__sub__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__sub__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">-</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.truediv"> <tt class="descclassname">operator.</tt><tt class="descname">truediv</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.truediv" title="Permalink to this definition">¶</a></dt> <dt id="operator.__truediv__"> <tt class="descclassname">operator.</tt><tt class="descname">__truediv__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__truediv__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">/</span> <span class="pre">b</span></tt> where 2/3 is .66 rather than 0. This is also known as “true” division.</p> </dd></dl> <dl class="function"> <dt id="operator.xor"> <tt class="descclassname">operator.</tt><tt class="descname">xor</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.xor" title="Permalink to this definition">¶</a></dt> <dt id="operator.__xor__"> <tt class="descclassname">operator.</tt><tt class="descname">__xor__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__xor__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the bitwise exclusive or of <em>a</em> and <em>b</em>.</p> </dd></dl> <p>Operations which work with sequences (some of them with mappings too) include:</p> <dl class="function"> <dt id="operator.concat"> <tt class="descclassname">operator.</tt><tt class="descname">concat</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.concat" title="Permalink to this definition">¶</a></dt> <dt id="operator.__concat__"> <tt class="descclassname">operator.</tt><tt class="descname">__concat__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__concat__" title="Permalink to this definition">¶</a></dt> <dd><p>Return <tt class="docutils literal"><span class="pre">a</span> <span class="pre">+</span> <span class="pre">b</span></tt> for <em>a</em> and <em>b</em> sequences.</p> </dd></dl> <dl class="function"> <dt id="operator.contains"> <tt class="descclassname">operator.</tt><tt class="descname">contains</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.contains" title="Permalink to this definition">¶</a></dt> <dt id="operator.__contains__"> <tt class="descclassname">operator.</tt><tt class="descname">__contains__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__contains__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the outcome of the test <tt class="docutils literal"><span class="pre">b</span> <span class="pre">in</span> <span class="pre">a</span></tt>. Note the reversed operands.</p> </dd></dl> <dl class="function"> <dt id="operator.countOf"> <tt class="descclassname">operator.</tt><tt class="descname">countOf</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.countOf" title="Permalink to this definition">¶</a></dt> <dd><p>Return the number of occurrences of <em>b</em> in <em>a</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.delitem"> <tt class="descclassname">operator.</tt><tt class="descname">delitem</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.delitem" title="Permalink to this definition">¶</a></dt> <dt id="operator.__delitem__"> <tt class="descclassname">operator.</tt><tt class="descname">__delitem__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__delitem__" title="Permalink to this definition">¶</a></dt> <dd><p>Remove the value of <em>a</em> at index <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.getitem"> <tt class="descclassname">operator.</tt><tt class="descname">getitem</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.getitem" title="Permalink to this definition">¶</a></dt> <dt id="operator.__getitem__"> <tt class="descclassname">operator.</tt><tt class="descname">__getitem__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__getitem__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the value of <em>a</em> at index <em>b</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.indexOf"> <tt class="descclassname">operator.</tt><tt class="descname">indexOf</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.indexOf" title="Permalink to this definition">¶</a></dt> <dd><p>Return the index of the first of occurrence of <em>b</em> in <em>a</em>.</p> </dd></dl> <dl class="function"> <dt id="operator.setitem"> <tt class="descclassname">operator.</tt><tt class="descname">setitem</tt><big>(</big><em>a</em>, <em>b</em>, <em>c</em><big>)</big><a class="headerlink" href="#operator.setitem" title="Permalink to this definition">¶</a></dt> <dt id="operator.__setitem__"> <tt class="descclassname">operator.</tt><tt class="descname">__setitem__</tt><big>(</big><em>a</em>, <em>b</em>, <em>c</em><big>)</big><a class="headerlink" href="#operator.__setitem__" title="Permalink to this definition">¶</a></dt> <dd><p>Set the value of <em>a</em> at index <em>b</em> to <em>c</em>.</p> </dd></dl> <p>Example: Build a dictionary that maps the ordinals from <tt class="docutils literal"><span class="pre">0</span></tt> to <tt class="docutils literal"><span class="pre">255</span></tt> to their character equivalents.</p> <div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="p">{}</span> <span class="gp">>>> </span><span class="n">keys</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">256</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">vals</span> <span class="o">=</span> <span class="nb">map</span><span class="p">(</span><span class="nb">chr</span><span class="p">,</span> <span class="n">keys</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">map</span><span class="p">(</span><span class="n">operator</span><span class="o">.</span><span class="n">setitem</span><span class="p">,</span> <span class="p">[</span><span class="n">d</span><span class="p">]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">),</span> <span class="n">keys</span><span class="p">,</span> <span class="n">vals</span><span class="p">)</span> </pre></div> </div> <p>The <a class="reference internal" href="#module-operator" title="operator: Functions corresponding to the standard operators."><tt class="xref py py-mod docutils literal"><span class="pre">operator</span></tt></a> module also defines tools for generalized attribute and item lookups. These are useful for making fast field extractors as arguments for <a class="reference internal" href="functions.html#map" title="map"><tt class="xref py py-func docutils literal"><span class="pre">map()</span></tt></a>, <a class="reference internal" href="functions.html#sorted" title="sorted"><tt class="xref py py-func docutils literal"><span class="pre">sorted()</span></tt></a>, <a class="reference internal" href="itertools.html#itertools.groupby" title="itertools.groupby"><tt class="xref py py-meth docutils literal"><span class="pre">itertools.groupby()</span></tt></a>, or other functions that expect a function argument.</p> <dl class="function"> <dt id="operator.attrgetter"> <tt class="descclassname">operator.</tt><tt class="descname">attrgetter</tt><big>(</big><em>attr</em><big>)</big><a class="headerlink" href="#operator.attrgetter" title="Permalink to this definition">¶</a></dt> <dt> <tt class="descclassname">operator.</tt><tt class="descname">attrgetter</tt><big>(</big><em>*attrs</em><big>)</big></dt> <dd><p>Return a callable object that fetches <em>attr</em> from its operand. If more than one attribute is requested, returns a tuple of attributes. The attribute names can also contain dots. For example:</p> <ul class="simple"> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">attrgetter('name')</span></tt>, the call <tt class="docutils literal"><span class="pre">f(b)</span></tt> returns <tt class="docutils literal"><span class="pre">b.name</span></tt>.</li> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">attrgetter('name',</span> <span class="pre">'date')</span></tt>, the call <tt class="docutils literal"><span class="pre">f(b)</span></tt> returns <tt class="docutils literal"><span class="pre">(b.name,</span> <span class="pre">b.date)</span></tt>.</li> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">attrgetter('name.first',</span> <span class="pre">'name.last')</span></tt>, the call <tt class="docutils literal"><span class="pre">f(b)</span></tt> returns <tt class="docutils literal"><span class="pre">(r.name.first,</span> <span class="pre">r.name.last)</span></tt>.</li> </ul> <p>Equivalent to:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="k">def</span> <span class="nf">attrgetter</span><span class="p">(</span><span class="o">*</span><span class="n">items</span><span class="p">):</span> <span class="k">if</span> <span class="nb">any</span><span class="p">(</span><span class="ow">not</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">item</span><span class="p">,</span> <span class="nb">str</span><span class="p">)</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">items</span><span class="p">):</span> <span class="k">raise</span> <span class="ne">TypeError</span><span class="p">(</span><span class="s">'attribute name must be a string'</span><span class="p">)</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">items</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">:</span> <span class="n">attr</span> <span class="o">=</span> <span class="n">items</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span> <span class="k">return</span> <span class="n">resolve_attr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">attr</span><span class="p">)</span> <span class="k">else</span><span class="p">:</span> <span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span> <span class="k">return</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">resolve_att</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">attr</span><span class="p">)</span> <span class="k">for</span> <span class="n">attr</span> <span class="ow">in</span> <span class="n">items</span><span class="p">)</span> <span class="k">return</span> <span class="n">g</span> <span class="k">def</span> <span class="nf">resolve_attr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">attr</span><span class="p">):</span> <span class="k">for</span> <span class="n">name</span> <span class="ow">in</span> <span class="n">attr</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s">"."</span><span class="p">):</span> <span class="n">obj</span> <span class="o">=</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">name</span><span class="p">)</span> <span class="k">return</span> <span class="n">obj</span> </pre></div> </div> </dd></dl> <dl class="function"> <dt id="operator.itemgetter"> <tt class="descclassname">operator.</tt><tt class="descname">itemgetter</tt><big>(</big><em>item</em><big>)</big><a class="headerlink" href="#operator.itemgetter" title="Permalink to this definition">¶</a></dt> <dt> <tt class="descclassname">operator.</tt><tt class="descname">itemgetter</tt><big>(</big><em>*items</em><big>)</big></dt> <dd><p>Return a callable object that fetches <em>item</em> from its operand using the operand’s <a class="reference internal" href="#operator.__getitem__" title="operator.__getitem__"><tt class="xref py py-meth docutils literal"><span class="pre">__getitem__()</span></tt></a> method. If multiple items are specified, returns a tuple of lookup values. For example:</p> <ul class="simple"> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">itemgetter(2)</span></tt>, the call <tt class="docutils literal"><span class="pre">f(r)</span></tt> returns <tt class="docutils literal"><span class="pre">r[2]</span></tt>.</li> <li>After <tt class="docutils literal"><span class="pre">g</span> <span class="pre">=</span> <span class="pre">itemgetter(2,</span> <span class="pre">5,</span> <span class="pre">3)</span></tt>, the call <tt class="docutils literal"><span class="pre">g(r)</span></tt> returns <tt class="docutils literal"><span class="pre">(r[2],</span> <span class="pre">r[5],</span> <span class="pre">r[3])</span></tt>.</li> </ul> <p>Equivalent to:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="k">def</span> <span class="nf">itemgetter</span><span class="p">(</span><span class="o">*</span><span class="n">items</span><span class="p">):</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">items</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">:</span> <span class="n">item</span> <span class="o">=</span> <span class="n">items</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span> <span class="k">return</span> <span class="n">obj</span><span class="p">[</span><span class="n">item</span><span class="p">]</span> <span class="k">else</span><span class="p">:</span> <span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span> <span class="k">return</span> <span class="nb">tuple</span><span class="p">(</span><span class="n">obj</span><span class="p">[</span><span class="n">item</span><span class="p">]</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">items</span><span class="p">)</span> <span class="k">return</span> <span class="n">g</span> </pre></div> </div> <p>The items can be any type accepted by the operand’s <a class="reference internal" href="#operator.__getitem__" title="operator.__getitem__"><tt class="xref py py-meth docutils literal"><span class="pre">__getitem__()</span></tt></a> method. Dictionaries accept any hashable value. Lists, tuples, and strings accept an index or a slice:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">itemgetter</span><span class="p">(</span><span class="mi">1</span><span class="p">)(</span><span class="s">'ABCDEFG'</span><span class="p">)</span> <span class="go">'B'</span> <span class="gp">>>> </span><span class="n">itemgetter</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">5</span><span class="p">)(</span><span class="s">'ABCDEFG'</span><span class="p">)</span> <span class="go">('B', 'D', 'F')</span> <span class="gp">>>> </span><span class="n">itemgetter</span><span class="p">(</span><span class="nb">slice</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="k">None</span><span class="p">))(</span><span class="s">'ABCDEFG'</span><span class="p">)</span> <span class="go">'CDEFG'</span> </pre></div> </div> <p>Example of using <a class="reference internal" href="#operator.itemgetter" title="operator.itemgetter"><tt class="xref py py-func docutils literal"><span class="pre">itemgetter()</span></tt></a> to retrieve specific fields from a tuple record:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">inventory</span> <span class="o">=</span> <span class="p">[(</span><span class="s">'apple'</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="p">(</span><span class="s">'banana'</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="s">'pear'</span><span class="p">,</span> <span class="mi">5</span><span class="p">),</span> <span class="p">(</span><span class="s">'orange'</span><span class="p">,</span> <span class="mi">1</span><span class="p">)]</span> <span class="gp">>>> </span><span class="n">getcount</span> <span class="o">=</span> <span class="n">itemgetter</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">getcount</span><span class="p">,</span> <span class="n">inventory</span><span class="p">))</span> <span class="go">[3, 2, 5, 1]</span> <span class="gp">>>> </span><span class="nb">sorted</span><span class="p">(</span><span class="n">inventory</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="n">getcount</span><span class="p">)</span> <span class="go">[('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]</span> </pre></div> </div> </dd></dl> <dl class="function"> <dt id="operator.methodcaller"> <tt class="descclassname">operator.</tt><tt class="descname">methodcaller</tt><big>(</big><em>name</em><span class="optional">[</span>, <em>args...</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#operator.methodcaller" title="Permalink to this definition">¶</a></dt> <dd><p>Return a callable object that calls the method <em>name</em> on its operand. If additional arguments and/or keyword arguments are given, they will be given to the method as well. For example:</p> <ul class="simple"> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">methodcaller('name')</span></tt>, the call <tt class="docutils literal"><span class="pre">f(b)</span></tt> returns <tt class="docutils literal"><span class="pre">b.name()</span></tt>.</li> <li>After <tt class="docutils literal"><span class="pre">f</span> <span class="pre">=</span> <span class="pre">methodcaller('name',</span> <span class="pre">'foo',</span> <span class="pre">bar=1)</span></tt>, the call <tt class="docutils literal"><span class="pre">f(b)</span></tt> returns <tt class="docutils literal"><span class="pre">b.name('foo',</span> <span class="pre">bar=1)</span></tt>.</li> </ul> <p>Equivalent to:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="k">def</span> <span class="nf">methodcaller</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span> <span class="k">def</span> <span class="nf">caller</span><span class="p">(</span><span class="n">obj</span><span class="p">):</span> <span class="k">return</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">name</span><span class="p">)(</span><span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span> <span class="k">return</span> <span class="n">caller</span> </pre></div> </div> </dd></dl> <div class="section" id="mapping-operators-to-functions"> <span id="operator-map"></span><h2>10.3.1. Mapping Operators to Functions<a class="headerlink" href="#mapping-operators-to-functions" title="Permalink to this headline">¶</a></h2> <p>This table shows how abstract operations correspond to operator symbols in the Python syntax and the functions in the <a class="reference internal" href="#module-operator" title="operator: Functions corresponding to the standard operators."><tt class="xref py py-mod docutils literal"><span class="pre">operator</span></tt></a> module.</p> <table border="1" class="docutils"> <colgroup> <col width="26%" /> <col width="29%" /> <col width="45%" /> </colgroup> <thead valign="bottom"> <tr><th class="head">Operation</th> <th class="head">Syntax</th> <th class="head">Function</th> </tr> </thead> <tbody valign="top"> <tr><td>Addition</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">+</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">add(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Concatenation</td> <td><tt class="docutils literal"><span class="pre">seq1</span> <span class="pre">+</span> <span class="pre">seq2</span></tt></td> <td><tt class="docutils literal"><span class="pre">concat(seq1,</span> <span class="pre">seq2)</span></tt></td> </tr> <tr><td>Containment Test</td> <td><tt class="docutils literal"><span class="pre">obj</span> <span class="pre">in</span> <span class="pre">seq</span></tt></td> <td><tt class="docutils literal"><span class="pre">contains(seq,</span> <span class="pre">obj)</span></tt></td> </tr> <tr><td>Division</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">/</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">truediv(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Division</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">//</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">floordiv(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Bitwise And</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">&</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">and_(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Bitwise Exclusive Or</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">^</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">xor(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Bitwise Inversion</td> <td><tt class="docutils literal"><span class="pre">~</span> <span class="pre">a</span></tt></td> <td><tt class="docutils literal"><span class="pre">invert(a)</span></tt></td> </tr> <tr><td>Bitwise Or</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">|</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">or_(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Exponentiation</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">**</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">pow(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Identity</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">is</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">is_(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Identity</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">is</span> <span class="pre">not</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">is_not(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Indexed Assignment</td> <td><tt class="docutils literal"><span class="pre">obj[k]</span> <span class="pre">=</span> <span class="pre">v</span></tt></td> <td><tt class="docutils literal"><span class="pre">setitem(obj,</span> <span class="pre">k,</span> <span class="pre">v)</span></tt></td> </tr> <tr><td>Indexed Deletion</td> <td><tt class="docutils literal"><span class="pre">del</span> <span class="pre">obj[k]</span></tt></td> <td><tt class="docutils literal"><span class="pre">delitem(obj,</span> <span class="pre">k)</span></tt></td> </tr> <tr><td>Indexing</td> <td><tt class="docutils literal"><span class="pre">obj[k]</span></tt></td> <td><tt class="docutils literal"><span class="pre">getitem(obj,</span> <span class="pre">k)</span></tt></td> </tr> <tr><td>Left Shift</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre"><<</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">lshift(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Modulo</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">%</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">mod(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Multiplication</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">*</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">mul(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Negation (Arithmetic)</td> <td><tt class="docutils literal"><span class="pre">-</span> <span class="pre">a</span></tt></td> <td><tt class="docutils literal"><span class="pre">neg(a)</span></tt></td> </tr> <tr><td>Negation (Logical)</td> <td><tt class="docutils literal"><span class="pre">not</span> <span class="pre">a</span></tt></td> <td><tt class="docutils literal"><span class="pre">not_(a)</span></tt></td> </tr> <tr><td>Positive</td> <td><tt class="docutils literal"><span class="pre">+</span> <span class="pre">a</span></tt></td> <td><tt class="docutils literal"><span class="pre">pos(a)</span></tt></td> </tr> <tr><td>Right Shift</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">>></span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">rshift(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Slice Assignment</td> <td><tt class="docutils literal"><span class="pre">seq[i:j]</span> <span class="pre">=</span> <span class="pre">values</span></tt></td> <td><tt class="docutils literal"><span class="pre">setitem(seq,</span> <span class="pre">slice(i,</span> <span class="pre">j),</span> <span class="pre">values)</span></tt></td> </tr> <tr><td>Slice Deletion</td> <td><tt class="docutils literal"><span class="pre">del</span> <span class="pre">seq[i:j]</span></tt></td> <td><tt class="docutils literal"><span class="pre">delitem(seq,</span> <span class="pre">slice(i,</span> <span class="pre">j))</span></tt></td> </tr> <tr><td>Slicing</td> <td><tt class="docutils literal"><span class="pre">seq[i:j]</span></tt></td> <td><tt class="docutils literal"><span class="pre">getitem(seq,</span> <span class="pre">slice(i,</span> <span class="pre">j))</span></tt></td> </tr> <tr><td>String Formatting</td> <td><tt class="docutils literal"><span class="pre">s</span> <span class="pre">%</span> <span class="pre">obj</span></tt></td> <td><tt class="docutils literal"><span class="pre">mod(s,</span> <span class="pre">obj)</span></tt></td> </tr> <tr><td>Subtraction</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">-</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">sub(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Truth Test</td> <td><tt class="docutils literal"><span class="pre">obj</span></tt></td> <td><tt class="docutils literal"><span class="pre">truth(obj)</span></tt></td> </tr> <tr><td>Ordering</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre"><</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">lt(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Ordering</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre"><=</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">le(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Equality</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">eq(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Difference</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">!=</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">ne(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Ordering</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">>=</span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">ge(a,</span> <span class="pre">b)</span></tt></td> </tr> <tr><td>Ordering</td> <td><tt class="docutils literal"><span class="pre">a</span> <span class="pre">></span> <span class="pre">b</span></tt></td> <td><tt class="docutils literal"><span class="pre">gt(a,</span> <span class="pre">b)</span></tt></td> </tr> </tbody> </table> </div> <div class="section" id="inplace-operators"> <h2>10.3.2. Inplace Operators<a class="headerlink" href="#inplace-operators" title="Permalink to this headline">¶</a></h2> <p>Many operations have an “in-place” version. Listed below are functions providing a more primitive access to in-place operators than the usual syntax does; for example, the <a class="reference internal" href="../glossary.html#term-statement"><em class="xref std std-term">statement</em></a> <tt class="docutils literal"><span class="pre">x</span> <span class="pre">+=</span> <span class="pre">y</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">x</span> <span class="pre">=</span> <span class="pre">operator.iadd(x,</span> <span class="pre">y)</span></tt>. Another way to put it is to say that <tt class="docutils literal"><span class="pre">z</span> <span class="pre">=</span> <span class="pre">operator.iadd(x,</span> <span class="pre">y)</span></tt> is equivalent to the compound statement <tt class="docutils literal"><span class="pre">z</span> <span class="pre">=</span> <span class="pre">x;</span> <span class="pre">z</span> <span class="pre">+=</span> <span class="pre">y</span></tt>.</p> <p>In those examples, note that when an in-place method is called, the computation and assignment are performed in two separate steps. The in-place functions listed below only do the first step, calling the in-place method. The second step, assignment, is not handled.</p> <p>For immutable targets such as strings, numbers, and tuples, the updated value is computed, but not assigned back to the input variable:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="s">'hello'</span> <span class="gp">>>> </span><span class="n">iadd</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="s">' world'</span><span class="p">)</span> <span class="go">'hello world'</span> <span class="gp">>>> </span><span class="n">a</span> <span class="go">'hello'</span> </pre></div> </div> <p>For mutable targets such as lists and dictionaries, the inplace method will perform the update, so no subsequent assignment is necessary:</p> <div class="highlight-python3"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">s</span> <span class="o">=</span> <span class="p">[</span><span class="s">'h'</span><span class="p">,</span> <span class="s">'e'</span><span class="p">,</span> <span class="s">'l'</span><span class="p">,</span> <span class="s">'l'</span><span class="p">,</span> <span class="s">'o'</span><span class="p">]</span> <span class="gp">>>> </span><span class="n">iadd</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="p">[</span><span class="s">' '</span><span class="p">,</span> <span class="s">'w'</span><span class="p">,</span> <span class="s">'o'</span><span class="p">,</span> <span class="s">'r'</span><span class="p">,</span> <span class="s">'l'</span><span class="p">,</span> <span class="s">'d'</span><span class="p">])</span> <span class="go">['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']</span> <span class="gp">>>> </span><span class="n">s</span> <span class="go">['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']</span> </pre></div> </div> <dl class="function"> <dt id="operator.iadd"> <tt class="descclassname">operator.</tt><tt class="descname">iadd</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.iadd" title="Permalink to this definition">¶</a></dt> <dt id="operator.__iadd__"> <tt class="descclassname">operator.</tt><tt class="descname">__iadd__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__iadd__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">iadd(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">+=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.iand"> <tt class="descclassname">operator.</tt><tt class="descname">iand</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.iand" title="Permalink to this definition">¶</a></dt> <dt id="operator.__iand__"> <tt class="descclassname">operator.</tt><tt class="descname">__iand__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__iand__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">iand(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">&=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.iconcat"> <tt class="descclassname">operator.</tt><tt class="descname">iconcat</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.iconcat" title="Permalink to this definition">¶</a></dt> <dt id="operator.__iconcat__"> <tt class="descclassname">operator.</tt><tt class="descname">__iconcat__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__iconcat__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">iconcat(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">+=</span> <span class="pre">b</span></tt> for <em>a</em> and <em>b</em> sequences.</p> </dd></dl> <dl class="function"> <dt id="operator.ifloordiv"> <tt class="descclassname">operator.</tt><tt class="descname">ifloordiv</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ifloordiv" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ifloordiv__"> <tt class="descclassname">operator.</tt><tt class="descname">__ifloordiv__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ifloordiv__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">ifloordiv(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">//=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.ilshift"> <tt class="descclassname">operator.</tt><tt class="descname">ilshift</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ilshift" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ilshift__"> <tt class="descclassname">operator.</tt><tt class="descname">__ilshift__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ilshift__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">ilshift(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre"><<=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.imod"> <tt class="descclassname">operator.</tt><tt class="descname">imod</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.imod" title="Permalink to this definition">¶</a></dt> <dt id="operator.__imod__"> <tt class="descclassname">operator.</tt><tt class="descname">__imod__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__imod__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">imod(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">%=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.imul"> <tt class="descclassname">operator.</tt><tt class="descname">imul</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.imul" title="Permalink to this definition">¶</a></dt> <dt id="operator.__imul__"> <tt class="descclassname">operator.</tt><tt class="descname">__imul__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__imul__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">imul(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">*=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.ior"> <tt class="descclassname">operator.</tt><tt class="descname">ior</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ior" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ior__"> <tt class="descclassname">operator.</tt><tt class="descname">__ior__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ior__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">ior(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">|=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.ipow"> <tt class="descclassname">operator.</tt><tt class="descname">ipow</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ipow" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ipow__"> <tt class="descclassname">operator.</tt><tt class="descname">__ipow__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ipow__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">ipow(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">**=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.irshift"> <tt class="descclassname">operator.</tt><tt class="descname">irshift</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.irshift" title="Permalink to this definition">¶</a></dt> <dt id="operator.__irshift__"> <tt class="descclassname">operator.</tt><tt class="descname">__irshift__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__irshift__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">irshift(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">>>=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.isub"> <tt class="descclassname">operator.</tt><tt class="descname">isub</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.isub" title="Permalink to this definition">¶</a></dt> <dt id="operator.__isub__"> <tt class="descclassname">operator.</tt><tt class="descname">__isub__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__isub__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">isub(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">-=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.itruediv"> <tt class="descclassname">operator.</tt><tt class="descname">itruediv</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.itruediv" title="Permalink to this definition">¶</a></dt> <dt id="operator.__itruediv__"> <tt class="descclassname">operator.</tt><tt class="descname">__itruediv__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__itruediv__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">itruediv(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">/=</span> <span class="pre">b</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="operator.ixor"> <tt class="descclassname">operator.</tt><tt class="descname">ixor</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.ixor" title="Permalink to this definition">¶</a></dt> <dt id="operator.__ixor__"> <tt class="descclassname">operator.</tt><tt class="descname">__ixor__</tt><big>(</big><em>a</em>, <em>b</em><big>)</big><a class="headerlink" href="#operator.__ixor__" title="Permalink to this definition">¶</a></dt> <dd><p><tt class="docutils literal"><span class="pre">a</span> <span class="pre">=</span> <span class="pre">ixor(a,</span> <span class="pre">b)</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">a</span> <span class="pre">^=</span> <span class="pre">b</span></tt>.</p> </dd></dl> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">10.3. <tt class="docutils literal"><span class="pre">operator</span></tt> — Standard operators as functions</a><ul> <li><a class="reference internal" href="#mapping-operators-to-functions">10.3.1. Mapping Operators to Functions</a></li> <li><a class="reference internal" href="#inplace-operators">10.3.2. Inplace Operators</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="functools.html" title="previous chapter">10.2. <tt class="docutils literal docutils literal docutils literal"><span class="pre">functools</span></tt> — Higher-order functions and operations on callable objects</a></p> <h4>Next topic</h4> <p class="topless"><a href="filesys.html" title="next chapter">11. 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