diff --git a/pdf/index_for_pdf.html b/pdf/index_for_pdf.html
index cd2c530..2636523 100644
--- a/pdf/index_for_pdf.html
+++ b/pdf/index_for_pdf.html
@@ -119,7 +119,7 @@
 <h3 id="s">S</h3>
 <p><strong>scraping, <a href="#scraping">35</a>, <a href="#basicmariobrothersexample">43</a>, <a href="#encodedecode">46</a>, <a href="#coviddeathsbycontinent">47</a>-<a href="#confirmedcovidcasesdowjonesgoldandbitcoinprice">48</a></strong><br>
 <strong>sequence, <a href="#abstractbaseclasses">4</a>, <a href="#sequence">18</a>-<a href="#abcsequence">19</a></strong><br>
-<strong>sets, <a href="#set">2</a>, <a href="#abstractbaseclasses">4</a>, <a href="#otheruses">11</a>, <a href="#tableofrequiredandautomaticallyavailablespecialmethods">19</a>, <a href="#collectionsandtheirexceptions">21</a></strong><br>
+<strong>sets, <a href="#set">2</a>, <a href="#abstractbaseclasses">4</a>, <a href="#otheruses">11</a>, <a href="#tableofrequiredandautomaticallyavailablespecialmethods">19</a>, <a href="#collectionsandtheirexceptions">21</a>, <a href="#operator">31</a></strong><br>
 <strong>shell commands, <a href="#shellcommands">25</a></strong><br>
 <strong>sleep function, <a href="#progressbar">34</a></strong><br>
 <strong>slots attribute, <a href="#slots">15</a></strong><br>
diff --git a/pdf/index_for_pdf_print.html b/pdf/index_for_pdf_print.html
index d7d786d..2d0834d 100644
--- a/pdf/index_for_pdf_print.html
+++ b/pdf/index_for_pdf_print.html
@@ -119,7 +119,7 @@
 <h3 id="s">S</h3>
 <p><strong>scraping, 35, 43, 46, 47-48</strong><br>
 <strong>sequence, 4, 18-19</strong><br>
-<strong>sets, 2, 4, 11, 19, 21</strong><br>
+<strong>sets, 2, 4, 11, 19, 21, 31</strong><br>
 <strong>shell commands, 25</strong><br>
 <strong>sleep function, 34</strong><br>
 <strong>slots attribute, 15</strong><br>