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diff --git a/01-short-introduction-to-Python.html b/01-short-introduction-to-Python.html
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@@ -875,7 +875,7 @@ <h4 class="accordion-header" id="headingSolution2">
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index df53ad8e3..9cd518d82 100644
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-        <p> Last updated on 2023-05-19 | 
+        <p> Last updated on 2023-08-18 | 
         
         <a href="https://github.com/datacarpentry/python-ecology-lesson/edit/main/episodes/03-index-slice-subset.md" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
         
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-<code>surveys_df['species_id', 'plot_id', 'weight']</code>), while
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-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
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-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
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index 63bee2182..2490e990b 100644
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   "dateCreated": "2015-03-19",
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diff --git a/CONTRIBUTORS.html b/CONTRIBUTORS.html
index 1d930d7dc..0393bb229 100644
--- a/CONTRIBUTORS.html
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   "dateCreated": "2015-03-19",
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-  "datePublished": "2023-08-15"
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diff --git a/LICENSE.html b/LICENSE.html
index 05a44e9d6..94f329c63 100644
--- a/LICENSE.html
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diff --git a/aio.html b/aio.html
index 08eb474b0..bee52b63f 100644
--- a/aio.html
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   </h4>
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-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
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 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>What happens when you execute <code>a_list[1] = 5</code>?</li>
@@ -1286,7 +1286,7 @@ <h4 class="accordion-header" id="headingSolution2">
   Show me the solution
   </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
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 <hr>
-<p> Last updated on 2023-05-19 | 
+<p> Last updated on 2023-08-18 | 
         
         <a href="https://github.com/datacarpentry/python-ecology-lesson/edit/main/episodes/03-index-slice-subset.md" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
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 <ol style="list-style-type: decimal">
 <li><p><code>a[0]</code> returns <code>1</code>, as Python starts with
@@ -2895,7 +2895,7 @@ <h3 class="code-label">OUTPUT<i aria-hidden="true" data-feather="chevron-left"><
 with a single list of labels (or <code>iloc</code> with a single list of
 integers). However, unlike <code>loc</code> or <code>iloc</code>,
 indexing a data frame directly with labels will select columns (e.g.
-<code>surveys_df['species_id', 'plot_id', 'weight']</code>), while
+<code>surveys_df[['species_id', 'plot_id', 'weight']]</code>), while
 ranges of integers will select rows (e.g. surveys_df[0:13]). Direct
 indexing of rows is redundant with using <code>iloc</code>, and will
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@@ -2943,7 +2943,7 @@ <h4 class="accordion-header" id="headingSolution2">
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-<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
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 <div class="accordion-body">
 <p><code>surveys_df[::-1]</code> provides every row of the DataFrame, in
 reverse order.</p>
@@ -380,7 +380,7 @@ <h4 class="accordion-header" id="headingSolution2">
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 </button>
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 <p>We get the expected files for all years between 1977 and 2002, plus
 an empty <code>data/surveys1976.csv</code> file with only the
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@@ -877,7 +877,7 @@ <h4 class="accordion-header" id="headingSolution2">
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 <p>It can help to further demonstrate the freedom the user has to define
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         <h1>Indexing, Slicing and Subsetting DataFrames in Python</h1>
-        <p> Last updated on 2023-05-19 | 
+        <p> Last updated on 2023-08-18 | 
         
         <a href="https://github.com/datacarpentry/python-ecology-lesson/edit/main/episodes/03-index-slice-subset.md" class="external-link">Edit this page <i aria-hidden="true" data-feather="edit"></i></a></p>
         
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 with a single list of labels (or <code>iloc</code> with a single list of
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 indexing a data frame directly with labels will select columns (e.g.
-<code>surveys_df['species_id', 'plot_id', 'weight']</code>), while
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 <p>When working through the solutions to the challenges above, you could
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 <div class="accordion-body">
 <p>Referring to the challenge solution above, as we know the other
 values are all Nan values, we could also select all not null values:</p>
@@ -1310,8 +1310,8 @@ <h3 class="callout-title">Keypoints<a class="anchor" aria-label="anchor" href="#
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@@ -604,7 +604,7 @@ <h4 class="accordion-header" id="headingSolution1">
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-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
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 <div class="accordion-body">
 <p>The method <code>.count()</code> gives you the number of non-NaN
 observations per column. Try looking to the <code>.isna()</code>
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