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<h3>Augmented Assignment</h3>
<p>Python provides the following set of augmented assignment operators:</p>

<P><TABle boRDER="1" cellSPACing="0" cellpadding="1" width="100%">
<cOlgRoup Span="2">
<tR>
<th vALIGn="top">
<fonT SIZe="2">
<p><b>Operation</b></P>
</FONt></th>
<tH VALign="top">
<font size="2">
<p><b>Description</b></p>
</font></tH>
</tr>
<Tr>
<td ValigN="top">
<fonT SIZe="2">
<p><i><tT CLAss="monofont">x</tt></I>
<TT Class="monofont"> += </TT><I><Tt class="monofont">y</tt></i>
</p>
</font></td>
<td vaLigN="top">
<fonT size="2">
<P><i><tt CLASs="monofont">x</tt></i>
<TT CLass="monofont"> = </tT><I><TT clasS="monofont">x</TT></I>
<tt class="monofont"> + </tt><i><tt class="monofont">y</tt></i>
</P>
</foNt></td>
</Tr>
<tr>
<tD valIGN="top">
<Font sIZE="2">
<P><i><tt cLASS="monofont">x</tt></i>
<tT CLAss="monofont"> -= </tt><i><tt class="monofont">y</tt></i>
</p>
</font></Td>
<tD valIgn="top">
<foNt siZE="2">
<P><I><tt clASS="monofont">x</Tt></i>
<tt CLASs="monofont"> = </tt><i><TT CLass="monofont">x</tt></i>
<tt class="monofont"> - </tt><i><tt clAss="monofont">y</Tt></i>
</p>
</Font></tD>
</tr>
<tR>
<TD ValigN="top">
<FONt sizE="2">
<P><I><Tt claSS="monofont">x</TT></i>
<tt class="monofont"> *= </tt><i><tt class="monofont">y</tt></I>
</p>
</fOnt></tD>
<td vaLign="top">
<FONT size="2">
<P><I><TT clasS="monofont">x</TT></I>
<tt clASS="monofont"> = </Tt><i><tt class="monofont">x</tt></i>
<tt class="monofont"> * </tT><i><tT claSs="monofont">y</tt></i>
</P>
</fonT></TD>
</Tr>
<tr>
<tD VALign="top">
<fONT Size="2">
<p><I><TT Class="monofont">x</tt></i>
<tt class="monofont"> /= </tt><i><tt cLasS="monofont">y</tt></i>
</P>
</font></Td>
<td VALIgn="top">
<foNT SIze="2">
<p><i><TT CLass="monofont">x</tT></I>
<TT class="monofont"> = </tt><i><tt class="monofont">x</tt></i>
<tt ClaSs="monofont"> / </tt><I><tt clAss="monofont">y</tT></I>
</P>
</Font></tD>
</TR>
<Tr>
<td vALIGn="top">
<fonT SIZe="2">
<p><i><tt class="monofont">x</tt></i>
<tt class="monofont"> **= </Tt><i><Tt clAss="monofont">y</tt></I>
</p>
</foNT></TD>
<td vaLIGN="top">
<font SIZE="2">
<p><i><tt CLASs="monofont">x</tt></i>
<tt class="monofont"> = </tt><i><tt clasS="monofont">x</tt></I>
<tt cLass="monofont"> ** </tT><i><tt CLASs="monofont">y</tt></i>
</P>
</FONt></td>
</tR>
<TR>
<Td valIGN="top">
<Font size="2">
<p><i><tt class="monofont">x</tt></i>
<tT clAss="monofont"> %= </tT><i><tt cLass="monofont">y</TT></I>
</P>
</font></TD>
<TD valiGN="top">
<FOnt siZE="2">
<P><I><tt class="monofont">x</tt></i>
<tt class="monofont"> = </tt><i><Tt cLass="monofont">x</Tt></i>
<tt ClasS="monofont"> % </TT><I><tt clASS="monofont">y</Tt></i>
</p>
</fONT></Td>
</tr>
<tR>
<TD Valign="top">
<font size="2">
<p><i><tt claSs="monofont">x</tT></i>
<tt Class="monofont"> &amp;= </Tt><i><tT CLAss="monofont">y</tt></I>
</P>
</FOnt></td>
<TD VAlign="top">
<FONT size="2">
<p><i><tt class="monofont">x</tt></i>
<tt clAss="monofont"> = </Tt><i><tT clasS="monofont">x</tt></i>
<TT CLass="monofont"> &amp; </tT><I><TT clasS="monofont">y</TT></I>
</p>
</fonT></TD>
</Tr>
<tr>
<td valign="top">
<font size="2">
<p><I><tt ClasS="monofont">x</tt></i>
<tT claSS="monofont"> |= </TT><i><tt cLASS="monofont">y</tt></i>
</p>
</FONT></td>
<td VALIgn="top">
<font size="2">
<p><i><tt class="monofont">x</tT></i>
<tT claSs="monofont"> = </tt><i><Tt clASS="monofont">x</Tt></i>
<tt CLASs="monofont"> | </tt><i><TT CLass="monofont">y</tT></I>
</P>
</Font></td>
</tr>
<tr>
<td valign="top">
<fonT siZe="2">
<p><i><Tt claSs="monofont">x</tt></I>
<TT Class="monofont"> ^= </TT><I><Tt claSS="monofont">y</TT></i>
</p>
</foNT></TD>
<td valign="top">
<font size="2">
<p><i><tt ClaSs="monofont">x</tt></I>
<tt clAss="monofont"> = </tT><I><TT clasS="monofont">x</TT></I>
<tt clASS="monofont"> ^ </Tt><i><tt CLASs="monofont">y</tt></i>
</p>
</font></td>
</tr>
<tr>
<td valIgn="top">
<Font Size="2">
<p><I><tt cLASS="monofont">x</tt></i>
<tT CLAss="monofont"> &gt;&gt;= </tt><I><TT Class="monofont">y</TT></I>
</P>
</font></td>
<td valign="top">
<font siZe="2">
<p><I><tt cLass="monofont">x</tT></i>
<tt CLASs="monofont"> = </tt><i><TT CLass="monofont">x</tT></I>
<TT clasS="monofont"> &gt;&gt; </TT><I><tt class="monofont">y</tt></i>
</p>
</font></td>
</tr>
<tR>
<td ValiGn="top">
<fonT sizE="2">
<P><I><Tt claSS="monofont">x</TT></i>
<tt cLASS="monofont"> &lt;&lt;= </tt><i><tT CLAss="monofont">y</tt></i>
</p>
</font></td>
<td valign="top">
<FonT sizE="2">
<p><i><tt ClasS="monofont">x</TT></I>
<tt clASS="monofont"> = </Tt><i><tt CLASs="monofont">x</tt></i>
<TT CLass="monofont"> &lt;&lt; </tt><i><tt class="monofont">y</tt></i>
</p>
</fonT></td>
</Tr>
</coLgrouP>
</tabLE></P>

<P>These operators can be used anywhere that ordinary assignment is used. For example:</p>

<pre>

a = 3 
b = [1,2] 
c = "%s %s" 
a += 1                      # a = 4 
b[1] += 10                  # b = [1, 12] 
c %= ("Douglas", "Adams")    # c = "Douglas Adams" </PRE>

<P>Augmented assignment doesn抰 violate mutability or perform in-place modification of objects. Therefore, writing <i><tt cLASS="monofont">x</tt></i>
<tT CLAss="monofont"> += </tt><i><tt class="monofont">y</tt></i>
 creates an entirely new object <i><tt clAss="monofont">x</Tt></i>
 with the value <i><Tt claSs="monofont">x</tt></I>
<TT Class="monofont"> + </TT><I><Tt claSS="monofont">y</TT></i>
. User-defined classes can redefine the augmented assignment operators using the special methods described in <a hrEF="33.html">Chapter 3</A>, 揟ypes and Objects.
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