Added some exercises

2016-07-14 11:55:31 -05:00
parent 26f1f77460
commit 03ccfbdd33
2 changed files with 234 additions and 87 deletions
--- a/README.html
+++ b/README.html
@@ -4,12 +4,12 @@
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 <meta name="generator" content="Docutils 0.12: http://docutils.sourceforge.net/" />
-<title>100 numpy exercises</title>
+<title>100 numpy exercises</title>
 <link rel="stylesheet" href="numpy.css" type="text/css" />
 </head>
 <body>
 <div class="document" id="numpy-exercises">
-<h1 class="title">100 numpy exercises</h1>
+<h1 class="title">100 numpy exercises</h1>
 <h2 class="subtitle" id="a-joint-effort-of-the-numpy-community">A joint effort of the numpy community</h2>
 <p>The goal is both to offer a quick reference for new and old users and to
@@ -48,7 +48,7 @@ is:</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to get the documentation of the numpy add function from the command line ? (★☆☆)</p>
+<li><p class="first">How to get the documentation of the numpy add function from the command line? (★☆☆)</p>
 <pre class="code bash literal-block">
 python -c <span class="literal string double">&quot;import numpy; numpy.info(numpy.add)&quot;</span>
 </pre>
@@ -116,7 +116,7 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
 <span class="name">Z</span><span class="punctuation">[</span><span class="literal number integer">1</span><span class="punctuation">:</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">,</span><span class="literal number integer">1</span><span class="punctuation">:</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="literal number integer">0</span>
 </pre>
 </li>
-<li><p class="first">What is the result of the following expression ? (★☆☆)</p>
+<li><p class="first">What is the result of the following expression? (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="literal number integer">0</span> <span class="operator">*</span> <span class="name">np</span><span class="operator">.</span><span class="name">nan</span>
 <span class="name">np</span><span class="operator">.</span><span class="name">nan</span> <span class="operator">==</span> <span class="name">np</span><span class="operator">.</span><span class="name">nan</span>
@@ -139,7 +139,7 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element ?</p>
+<li><p class="first">Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?</p>
 <pre class="code python literal-block">
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">unravel_index</span><span class="punctuation">(</span><span class="literal number integer">100</span><span class="punctuation">,(</span><span class="literal number integer">6</span><span class="punctuation">,</span><span class="literal number integer">7</span><span class="punctuation">,</span><span class="literal number integer">8</span><span class="punctuation">)))</span>
 </pre>
@@ -158,6 +158,14 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
 <li><p class="first">Create a custom dtype that describes a color as four unisgned bytes (RGBA) (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="name">color</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dtype</span><span class="punctuation">([(</span><span class="literal string double">&quot;r&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
                  <span class="punctuation">(</span><span class="literal string double">&quot;g&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
                  <span class="punctuation">(</span><span class="literal string double">&quot;b&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
                  <span class="punctuation">(</span><span class="literal string double">&quot;a&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">)])</span>
 </pre>
 </li>
 <li><p class="first">Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dot</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">)),</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">)))</span>
@@ -172,6 +180,53 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
 <span class="name">Z</span><span class="punctuation">[(</span><span class="literal number integer">3</span> <span class="operator">&lt;</span> <span class="name">Z</span><span class="punctuation">)</span> <span class="operator">&amp;</span> <span class="punctuation">(</span><span class="name">Z</span> <span class="operator">&lt;=</span> <span class="literal number integer">8</span><span class="punctuation">)]</span> <span class="operator">*=</span> <span class="operator">-</span><span class="literal number integer">1</span>
 </pre>
 </li>
 <li><p class="first">What is the output of the following script? (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Jake VanderPlas</span>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name builtin">sum</span><span class="punctuation">(</span><span class="name builtin">range</span><span class="punctuation">(</span><span class="literal number integer">5</span><span class="punctuation">),</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">))</span>
 <span class="keyword namespace">from</span> <span class="name namespace">numpy</span> <span class="keyword namespace">import</span> <span class="operator">*</span>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name builtin">sum</span><span class="punctuation">(</span><span class="name builtin">range</span><span class="punctuation">(</span><span class="literal number integer">5</span><span class="punctuation">),</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">))</span>
 </pre>
 </li>
 <li><p class="first">Consider an integer vector Z, which of these expressions are legal? (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span><span class="operator">**</span><span class="name">Z</span>
 <span class="literal number integer">2</span> <span class="operator">&lt;&lt;</span> <span class="name">Z</span> <span class="operator">&gt;&gt;</span> <span class="literal number integer">2</span>
 <span class="name">Z</span> <span class="operator">&lt;-</span> <span class="name">Z</span>
 <span class="literal number integer">1j</span><span class="operator">*</span><span class="name">Z</span>
 <span class="name">Z</span><span class="operator">/</span><span class="literal number integer">1</span><span class="operator">/</span><span class="literal number integer">1</span>
 <span class="name">Z</span><span class="operator">&lt;</span><span class="name">Z</span><span class="operator">&gt;</span><span class="name">Z</span>
 </pre>
 </li>
 <li><p class="first">What are the result of the following expressions?</p>
 <pre class="code python literal-block">
 <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">//</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span>
 <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">//</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number float">0.</span><span class="punctuation">)</span>
 <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">/</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span>
 <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">/</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number float">0.</span><span class="punctuation">)</span>
 </pre>
 </li>
 <li><p class="first">How to round away from zero a float array ? (★☆☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Charles R Harris</span>
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="operator">+</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">)</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">trunc</span><span class="punctuation">(</span><span class="name">Z</span> <span class="operator">+</span> <span class="name">np</span><span class="operator">.</span><span class="name">copysign</span><span class="punctuation">(</span><span class="literal number float">0.5</span><span class="punctuation">,</span> <span class="name">Z</span><span class="punctuation">)))</span>
 </pre>
 </li>
 <li><p class="first">Extract the integer part of a random array using 5 different methods (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">)</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span> <span class="operator">-</span> <span class="name">Z</span><span class="operator">%</span><span class="literal number integer">1</span><span class="punctuation">)</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">floor</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">))</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ceil</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">)</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name builtin">int</span><span class="punctuation">))</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">trunc</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">))</span>
 </pre>
 </li>
 <li><p class="first">Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">zeros</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">5</span><span class="punctuation">))</span>
@@ -202,7 +257,7 @@ array (★☆☆)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to sum a small array faster than np.sum ? (★★☆)</p>
+<li><p class="first">How to sum a small array faster than np.sum? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Evgeni Burovski</span>
@@ -273,14 +328,14 @@ them to polar coordinates (★★☆)</p>
   <span class="keyword">print</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">finfo</span><span class="punctuation">(</span><span class="name">dtype</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">eps</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to print all the values of an array ?  (★★☆)</p>
+<li><p class="first">How to print all the values of an array?  (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">np</span><span class="operator">.</span><span class="name">set_printoptions</span><span class="punctuation">(</span><span class="name">threshold</span><span class="operator">=</span><span class="name">np</span><span class="operator">.</span><span class="name">nan</span><span class="punctuation">)</span>
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">zeros</span><span class="punctuation">((</span><span class="literal number integer">25</span><span class="punctuation">,</span><span class="literal number integer">25</span><span class="punctuation">))</span>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to find the closest value (to a given scalar) in an array ?  (★★☆)</p>
+<li><p class="first">How to find the closest value (to a given scalar) in an array?  (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">100</span><span class="punctuation">)</span>
 <span class="name">v</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">100</span><span class="punctuation">)</span>
@@ -316,24 +371,25 @@ point by point distances (★★☆)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">D</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to convert a float (32 bits) array into an integer (32 bits) in place ?</p>
+<li><p class="first">How to convert a float (32 bits) array into an integer (32 bits) in place?</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">10</span><span class="punctuation">,</span> <span class="name">dtype</span><span class="operator">=</span><span class="name">np</span><span class="operator">.</span><span class="name">int32</span><span class="punctuation">)</span>
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">float32</span><span class="punctuation">,</span> <span class="name">copy</span><span class="operator">=</span><span class="name builtin pseudo">False</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">Consider the following file:</p>
+<li><p class="first">How to read the following file? (★★☆)</p>
 <pre class="literal-block">
 1,2,3,4,5
 6,,,7,8
 ,,9,10,11
 </pre>
 <p>How to read it ? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># File content:</span>
 <span class="comment single"># -------------</span>
 <span class="literal number integer">1</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">4</span><span class="punctuation">,</span><span class="literal number integer">5</span>
 <span class="literal number integer">6</span><span class="punctuation">,,,</span><span class="literal number integer">7</span><span class="punctuation">,</span><span class="literal number integer">8</span>
 <span class="punctuation">,,</span><span class="literal number integer">9</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">11</span>
 <span class="comment single"># -------------</span>
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">genfromtxt</span><span class="punctuation">(</span><span class="literal string double">&quot;missing.dat&quot;</span><span class="punctuation">,</span> <span class="name">delimiter</span><span class="operator">=</span><span class="literal string double">&quot;,&quot;</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">What is the equivalent of <cite>enumerate</cite> for numpy arrays ? (★★☆)</p>
+<li><p class="first">What is the equivalent of <cite>enumerate</cite> for numpy arrays? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">9</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">reshape</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">)</span>
 <span class="keyword">for</span> <span class="name">index</span><span class="punctuation">,</span> <span class="name">value</span> <span class="operator word">in</span> <span class="name">np</span><span class="operator">.</span><span class="name">ndenumerate</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">):</span>
@@ -351,7 +407,7 @@ point by point distances (★★☆)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">G</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to randomly place p elements in a 2D array ? (★★☆)</p>
+<li><p class="first">How to randomly place p elements in a 2D array? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Divakar</span>
@@ -374,7 +430,7 @@ point by point distances (★★☆)</p>
 <span class="name">Y</span> <span class="operator">=</span> <span class="name">X</span> <span class="operator">-</span> <span class="name">X</span><span class="operator">.</span><span class="name">mean</span><span class="punctuation">(</span><span class="name">axis</span><span class="operator">=</span><span class="literal number integer">1</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">reshape</span><span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to I sort an array by the nth column ? (★★☆)</p>
+<li><p class="first">How to I sort an array by the nth column? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Steve Tjoa</span>
@@ -383,7 +439,7 @@ point by point distances (★★☆)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">[</span><span class="name">Z</span><span class="punctuation">[:,</span><span class="literal number integer">1</span><span class="punctuation">]</span><span class="operator">.</span><span class="name">argsort</span><span class="punctuation">()])</span>
 </pre>
 </li>
-<li><p class="first">How to tell if a given 2D array has null columns ? (★★☆)</p>
+<li><p class="first">How to tell if a given 2D array has null columns? (★★☆)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Warren Weckesser</span>
@@ -399,8 +455,23 @@ point by point distances (★★☆)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">m</span><span class="punctuation">)</span>
 </pre>
 </li>
 <li><p class="first">Create an array class that has a <cite>name</cite> attribute (★★☆)</p>
 <pre class="code python literal-block">
 <span class="keyword">class</span> <span class="name class">NamedArray</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ndarray</span><span class="punctuation">):</span>
    <span class="keyword">def</span> <span class="name function">__new__</span><span class="punctuation">(</span><span class="name">cls</span><span class="punctuation">,</span> <span class="name">array</span><span class="punctuation">,</span> <span class="name">name</span><span class="operator">=</span><span class="literal string double">&quot;no name&quot;</span><span class="punctuation">):</span>
        <span class="name">obj</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">asarray</span><span class="punctuation">(</span><span class="name">array</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">view</span><span class="punctuation">(</span><span class="name">cls</span><span class="punctuation">)</span>
        <span class="name">obj</span><span class="operator">.</span><span class="name">name</span> <span class="operator">=</span> <span class="name">name</span>
        <span class="keyword">return</span> <span class="name">obj</span>
    <span class="keyword">def</span> <span class="name function">__array_finalize__</span><span class="punctuation">(</span><span class="name builtin pseudo">self</span><span class="punctuation">,</span> <span class="name">obj</span><span class="punctuation">):</span>
        <span class="keyword">if</span> <span class="name">obj</span> <span class="operator word">is</span> <span class="name builtin pseudo">None</span><span class="punctuation">:</span> <span class="keyword">return</span>
        <span class="name builtin pseudo">self</span><span class="operator">.</span><span class="name">info</span> <span class="operator">=</span> <span class="name builtin">getattr</span><span class="punctuation">(</span><span class="name">obj</span><span class="punctuation">,</span> <span class="literal string single">'name'</span><span class="punctuation">,</span> <span class="literal string double">&quot;no name&quot;</span><span class="punctuation">)</span>
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">NamedArray</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">10</span><span class="punctuation">),</span> <span class="literal string double">&quot;range_10&quot;</span><span class="punctuation">)</span>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">name</span><span class="punctuation">)</span>
 </pre>
 </li>
 <li><p class="first">Consider a given vector, how to add 1 to each element indexed by a second
-vector (be careful with repeated indices) ? (★★★)</p>
+vector (be careful with repeated indices)? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Brett Olsen</span>
@@ -411,7 +482,7 @@ vector (be careful with repeated indices) ? (★★★)</p>
 </pre>
 </li>
 <li><p class="first">How to accumulate elements of a vector (X) to an array (F) based on an index
-list (I) ? (★★★)</p>
+list (I)? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Alan G Isaac</span>
@@ -434,7 +505,7 @@ colors (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Considering a four dimensions array, how to get sum over the last two axis
-at once ? (★★★)</p>
+at once? (★★★)</p>
 <pre class="code python literal-block">
 <span class="name">A</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">randint</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,(</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">4</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">4</span><span class="punctuation">))</span>
 <span class="name builtin">sum</span> <span class="operator">=</span> <span class="name">A</span><span class="operator">.</span><span class="name">reshape</span><span class="punctuation">(</span><span class="name">A</span><span class="operator">.</span><span class="name">shape</span><span class="punctuation">[:</span><span class="operator">-</span><span class="literal number integer">2</span><span class="punctuation">]</span> <span class="operator">+</span> <span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">,))</span><span class="operator">.</span><span class="name">sum</span><span class="punctuation">(</span><span class="name">axis</span><span class="operator">=-</span><span class="literal number integer">1</span><span class="punctuation">)</span>
@@ -442,7 +513,7 @@ at once ? (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Considering a one-dimensional vector D, how to compute means of subsets of D
-using a vector S of same size describing subset indices ? (★★★)</p>
+using a vector S of same size describing subset indices? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Jaime Fernández del Río</span>
@@ -454,7 +525,7 @@ using a vector S of same size describing subset indices ? (★★★)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">D_means</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to get the diagonal of a dot product ? (★★★)</p>
+<li><p class="first">How to get the diagonal of a dot product? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Mathieu Blondel</span>
@@ -469,7 +540,7 @@ using a vector S of same size describing subset indices ? (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3
-consecutive zeros interleaved between each value ?  (★★★)</p>
+consecutive zeros interleaved between each value?  (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Warren Weckesser</span>
@@ -481,14 +552,14 @@ consecutive zeros interleaved between each value ?  (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Consider an array of dimension (5,5,3), how to mulitply it by an array with
-dimensions (5,5) ?  (★★★)</p>
+dimensions (5,5)?  (★★★)</p>
 <pre class="code python literal-block">
 <span class="name">A</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">))</span>
 <span class="name">B</span> <span class="operator">=</span> <span class="literal number integer">2</span><span class="operator">*</span><span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">5</span><span class="punctuation">))</span>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">A</span> <span class="operator">*</span> <span class="name">B</span><span class="punctuation">[:,:,</span><span class="name builtin pseudo">None</span><span class="punctuation">])</span>
 </pre>
 </li>
-<li><p class="first">How to swap two rows of an array ? (★★★)</p>
+<li><p class="first">How to swap two rows of an array? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Eelco Hoogendoorn</span>
@@ -512,7 +583,7 @@ vertices), find the set of unique line segments composing all the triangles (★
 </pre>
 </li>
 <li><p class="first">Given an array C that is a bincount, how to produce an array A such that
-np.bincount(A) == C ?  (★★★)</p>
+np.bincount(A) == C?  (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Jaime Fernández del Río</span>
@@ -521,7 +592,7 @@ np.bincount(A) == C ?  (★★★)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">A</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to compute averages using a sliding window over an array ? (★★★)</p>
+<li><p class="first">How to compute averages using a sliding window over an array? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Jaime Fernández del Río</span>
@@ -548,7 +619,7 @@ row should be (Z[-3],Z[-2],Z[-1]) (★★★)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to negate a boolean, or to change the sign of a float inplace ? (★★★)</p>
+<li><p class="first">How to negate a boolean, or to change the sign of a float inplace? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Nathaniel J. Smith</span>
@@ -560,7 +631,7 @@ row should be (Z[-3],Z[-2],Z[-1]) (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Consider 2 sets of points P0,P1 describing lines (2d) and a point p, how to
-compute distance from p to each line i (P0[i],P1[i]) ? (★★★)</p>
+compute distance from p to each line i (P0[i],P1[i])? (★★★)</p>
 <pre class="code python literal-block">
 <span class="keyword">def</span> <span class="name function">distance</span><span class="punctuation">(</span><span class="name">P0</span><span class="punctuation">,</span> <span class="name">P1</span><span class="punctuation">,</span> <span class="name">p</span><span class="punctuation">):</span>
    <span class="name">T</span> <span class="operator">=</span> <span class="name">P1</span> <span class="operator">-</span> <span class="name">P0</span>
@@ -577,7 +648,7 @@ compute distance from p to each line i (P0[i],P1[i]) ? (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Consider 2 sets of points P0,P1 describing lines (2d) and a set of points P,
-how to compute distance from each point j (P[j]) to each line i (P0[i],P1[i]) ? (★★★)</p>
+how to compute distance from each point j (P[j]) to each line i (P0[i],P1[i])? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Italmassov Kuanysh</span>
 <span class="comment single"># based on distance function from previous question</span>
@@ -621,7 +692,7 @@ necessary)  (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Consider an array Z = [1,2,3,4,5,6,7,8,9,10,11,12,13,14], how to generate an
-array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]] ? (★★★)</p>
+array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]]? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Stefan van der Walt</span>
@@ -639,7 +710,7 @@ array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]] ? (★★★)</p
 <span class="name">rank</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">sum</span><span class="punctuation">(</span><span class="name">S</span> <span class="operator">&gt;</span> <span class="literal number float">1e-10</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to find the most frequent value in an array ?</p>
+<li><p class="first">How to find the most frequent value in an array?</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">randint</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">50</span><span class="punctuation">)</span>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">bincount</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">argmax</span><span class="punctuation">())</span>
@@ -676,7 +747,7 @@ array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]] ? (★★★)</p
 </pre>
 </li>
 <li><p class="first">Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1).
-How to compute the sum of of the p matrix products at once ? (result has shape (n,1)) (★★★)</p>
+How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Stefan van der Walt</span>
@@ -693,7 +764,7 @@ How to compute the sum of of the p matrix products at once ? (result has shape (
 <span class="comment single"># and 2 and 1, to remain with a (n,1) vector.</span>
 </pre>
 </li>
-<li><p class="first">Consider a 16x16 array, how to get the block-sum (block size is 4x4) ? (★★★)</p>
+<li><p class="first">Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Robert Kern</span>
@@ -703,7 +774,7 @@ How to compute the sum of of the p matrix products at once ? (result has shape (
                                       <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span> <span class="name">Z</span><span class="operator">.</span><span class="name">shape</span><span class="punctuation">[</span><span class="literal number integer">1</span><span class="punctuation">],</span> <span class="name">k</span><span class="punctuation">),</span> <span class="name">axis</span><span class="operator">=</span><span class="literal number integer">1</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">How to implement the Game of Life using numpy arrays ? (★★★)</p>
+<li><p class="first">How to implement the Game of Life using numpy arrays? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Nicolas Rougier</span>
@@ -757,7 +828,7 @@ combinations of every item) (★★★)</p>
 <span class="keyword">print</span> <span class="punctuation">(</span><span class="name">cartesian</span><span class="punctuation">(([</span><span class="literal number integer">1</span><span class="punctuation">,</span> <span class="literal number integer">2</span><span class="punctuation">,</span> <span class="literal number integer">3</span><span class="punctuation">],</span> <span class="punctuation">[</span><span class="literal number integer">4</span><span class="punctuation">,</span> <span class="literal number integer">5</span><span class="punctuation">],</span> <span class="punctuation">[</span><span class="literal number integer">6</span><span class="punctuation">,</span> <span class="literal number integer">7</span><span class="punctuation">])))</span>
 </pre>
 </li>
-<li><p class="first">How to create a record array from a regular array ? (★★★)</p>
+<li><p class="first">How to create a record array from a regular array? (★★★)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">([(</span><span class="literal string double">&quot;Hello&quot;</span><span class="punctuation">,</span> <span class="literal number float">2.5</span><span class="punctuation">,</span> <span class="literal number integer">3</span><span class="punctuation">),</span>
              <span class="punctuation">(</span><span class="literal string double">&quot;World&quot;</span><span class="punctuation">,</span> <span class="literal number float">3.6</span><span class="punctuation">,</span> <span class="literal number integer">2</span><span class="punctuation">)])</span>
@@ -766,7 +837,7 @@ combinations of every item) (★★★)</p>
                               <span class="name">formats</span> <span class="operator">=</span> <span class="literal string single">'S8, f8, i8'</span><span class="punctuation">)</span>
 </pre>
 </li>
-<li><p class="first">Comsider a large vector Z, compute Z to the power of 3 using 3 different
+<li><p class="first">Consider a large vector Z, compute Z to the power of 3 using 3 different
 methods (★★★)</p>
 <pre class="code python literal-block">
 <span class="name">Author</span><span class="punctuation">:</span> <span class="name">Ryan</span> <span class="name">G</span><span class="operator">.</span>
@@ -785,7 +856,7 @@ methods (★★★)</p>
 </li>
 <li><p class="first">Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A
 that contain elements of each row of B regardless of the order of the elements
-in B ? (★★★)</p>
+in B? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Gabe Schwartz</span>
@@ -822,7 +893,7 @@ in B ? (★★★)</p>
 <span class="keyword">print</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">unpackbits</span><span class="punctuation">(</span><span class="name">I</span><span class="punctuation">[:,</span> <span class="name">np</span><span class="operator">.</span><span class="name">newaxis</span><span class="punctuation">],</span> <span class="name">axis</span><span class="operator">=</span><span class="literal number integer">1</span><span class="punctuation">))</span>
 </pre>
 </li>
-<li><p class="first">Given a two dimensional array, how to extract unique rows ? (★★★)</p>
+<li><p class="first">Given a two dimensional array, how to extract unique rows? (★★★)</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Jaime Fernández del Río</span>
@@ -846,7 +917,7 @@ sum, and mul function (★★★)</p>
 </pre>
 </li>
 <li><p class="first">Considering a path described by two vectors (X,Y), how to sample it using
-equidistant samples (★★★) ?</p>
+equidistant samples (★★★)?</p>
 <pre class="code python literal-block">
 <span class="comment single"># Author: Bas Swinckels</span>
--- a/README.rst
+++ b/README.rst
@@ -52,7 +52,7 @@ Thanks to Michiaki Ariga, there is now a
      print(Z)
-#. How to get the documentation of the numpy add function from the command line ? (★☆☆) 
+#. How to get the documentation of the numpy add function from the command line? (★☆☆) 
   .. code-block:: bash
@@ -142,7 +142,7 @@ Thanks to Michiaki Ariga, there is now a
      Z[1:-1,1:-1] = 0
-#. What is the result of the following expression ? (★☆☆)
+#. What is the result of the following expression? (★☆☆)
   .. code-block:: python
@@ -170,7 +170,7 @@ Thanks to Michiaki Ariga, there is now a
      Z[::2,1::2] = 1
      print(Z)
-#. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element ?
+#. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
   .. code-block:: python
@@ -193,6 +193,14 @@ Thanks to Michiaki Ariga, there is now a
      Z = (Z - Zmin)/(Zmax - Zmin)
      print(Z)
 #. Create a custom dtype that describes a color as four unisgned bytes (RGBA) (★☆☆) 
   .. code-block:: python
      color = np.dtype([("r", np.ubyte, 1),
                        ("g", np.ubyte, 1),
                        ("b", np.ubyte, 1),
                        ("a", np.ubyte, 1)])
 #. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) 
@@ -210,6 +218,59 @@ Thanks to Michiaki Ariga, there is now a
      Z = np.arange(11)
      Z[(3 < Z) & (Z <= 8)] *= -1
 #. What is the output of the following script? (★☆☆)
   .. code-block:: python
      # Author: Jake VanderPlas
      print(sum(range(5),-1))
      from numpy import *
      print(sum(range(5),-1))
 #. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
   .. code-block:: python
      Z**Z
      2 << Z >> 2
      Z <- Z
      1j*Z
      Z/1/1
      Z<Z>Z
 #. What are the result of the following expressions?
   .. code-block:: python
      np.array(0) // np.array(0)
      np.array(0) // np.array(0.)
      np.array(0) / np.array(0)
      np.array(0) / np.array(0.)
 #. How to round away from zero a float array ? (★☆☆)
   .. code-block:: python
      # Author: Charles R Harris
      Z = np.random.uniform(-10,+10,10)
      print (np.trunc(Z + np.copysign(0.5, Z)))
 #. Extract the integer part of a random array using 5 different methods (★★☆)
   .. code-block:: python
      Z = np.random.uniform(0,10,10)
      print (Z - Z%1)
      print (np.floor(Z))
      print (np.ceil(Z)-1)
      print (Z.astype(int))
      print (np.trunc(Z))
 #. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) 
@@ -249,7 +310,7 @@ Thanks to Michiaki Ariga, there is now a
    print(Z)
-#. How to sum a small array faster than np.sum ? (★★☆) 
+#. How to sum a small array faster than np.sum? (★★☆) 
   .. code-block:: python
@@ -336,7 +397,7 @@ Thanks to Michiaki Ariga, there is now a
         print(np.finfo(dtype).max)
         print(np.finfo(dtype).eps)
-#. How to print all the values of an array ?  (★★☆)
+#. How to print all the values of an array?  (★★☆)
   .. code-block:: python
@@ -345,7 +406,7 @@ Thanks to Michiaki Ariga, there is now a
      print(Z)
-#. How to find the closest value (to a given scalar) in an array ?  (★★☆)
+#. How to find the closest value (to a given scalar) in an array?  (★★☆)
   .. code-block:: python
@@ -386,7 +447,7 @@ Thanks to Michiaki Ariga, there is now a
      print(D)
-#. How to convert a float (32 bits) array into an integer (32 bits) in place ?
+#. How to convert a float (32 bits) array into an integer (32 bits) in place?
   .. code-block:: python
@@ -394,20 +455,21 @@ Thanks to Michiaki Ariga, there is now a
      Z = Z.astype(np.float32, copy=False)
-#. Consider the following file::
+#. How to read the following file? (★★☆)
   .. code-block:: python
      # File content:
      # -------------
      1,2,3,4,5
      6,,,7,8
      ,,9,10,11
-
+      # -------------
   How to read it ? (★★☆) 
   .. code-block:: python
      Z = np.genfromtxt("missing.dat", delimiter=",")
-#. What is the equivalent of `enumerate` for numpy arrays ? (★★☆)
+#. What is the equivalent of `enumerate` for numpy arrays? (★★☆)
   .. code-block:: python
@@ -428,7 +490,7 @@ Thanks to Michiaki Ariga, there is now a
      G = np.exp(-( (D-mu)**2 / ( 2.0 * sigma**2 ) ) )
      print(G)
-#. How to randomly place p elements in a 2D array ? (★★☆)
+#. How to randomly place p elements in a 2D array? (★★☆)
   .. code-block:: python
@@ -453,7 +515,7 @@ Thanks to Michiaki Ariga, there is now a
      # Older versions of numpy
      Y = X - X.mean(axis=1).reshape(-1, 1)
-#. How to I sort an array by the nth column ? (★★☆) 
+#. How to I sort an array by the nth column? (★★☆) 
   .. code-block:: python
@@ -464,7 +526,7 @@ Thanks to Michiaki Ariga, there is now a
      print(Z[Z[:,1].argsort()])
-#. How to tell if a given 2D array has null columns ? (★★☆) 
+#. How to tell if a given 2D array has null columns? (★★☆) 
   .. code-block:: python
@@ -484,11 +546,26 @@ Thanks to Michiaki Ariga, there is now a
      print(m)
 #. Create an array class that has a `name` attribute (★★☆)
   .. code-block:: python
      class NamedArray(np.ndarray):
          def __new__(cls, array, name="no name"):
              obj = np.asarray(array).view(cls)
              obj.name = name
              return obj
          def __array_finalize__(self, obj):
              if obj is None: return
              self.info = getattr(obj, 'name', "no name")
      Z = NamedArray(np.arange(10), "range_10")
      print (Z.name)
 #. Consider a given vector, how to add 1 to each element indexed by a second
-   vector (be careful with repeated indices) ? (★★★) 
+   vector (be careful with repeated indices)? (★★★) 
   .. code-block:: python
@@ -501,7 +578,7 @@ Thanks to Michiaki Ariga, there is now a
 #. How to accumulate elements of a vector (X) to an array (F) based on an index
-   list (I) ? (★★★) 
+   list (I)? (★★★) 
   .. code-block:: python
@@ -528,7 +605,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Considering a four dimensions array, how to get sum over the last two axis
-   at once ? (★★★)
+   at once? (★★★)
   .. code-block:: python
@@ -538,7 +615,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Considering a one-dimensional vector D, how to compute means of subsets of D
-   using a vector S of same size describing subset indices ? (★★★) 
+   using a vector S of same size describing subset indices? (★★★) 
   .. code-block:: python
@@ -552,7 +629,7 @@ Thanks to Michiaki Ariga, there is now a
      print(D_means)
-#. How to get the diagonal of a dot product ? (★★★) 
+#. How to get the diagonal of a dot product? (★★★) 
   .. code-block:: python
@@ -569,7 +646,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3
-   consecutive zeros interleaved between each value ?  (★★★) 
+   consecutive zeros interleaved between each value?  (★★★) 
   .. code-block:: python
@@ -583,7 +660,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider an array of dimension (5,5,3), how to mulitply it by an array with
-   dimensions (5,5) ?  (★★★) 
+   dimensions (5,5)?  (★★★) 
   .. code-block:: python
@@ -592,7 +669,7 @@ Thanks to Michiaki Ariga, there is now a
      print(A * B[:,:,None])
-#. How to swap two rows of an array ? (★★★) 
+#. How to swap two rows of an array? (★★★) 
   .. code-block:: python
@@ -620,7 +697,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Given an array C that is a bincount, how to produce an array A such that
-   np.bincount(A) == C ?  (★★★) 
+   np.bincount(A) == C?  (★★★) 
   .. code-block:: python
@@ -631,7 +708,7 @@ Thanks to Michiaki Ariga, there is now a
     print(A)
-#. How to compute averages using a sliding window over an array ? (★★★) 
+#. How to compute averages using a sliding window over an array? (★★★) 
   .. code-block:: python
@@ -661,7 +738,7 @@ Thanks to Michiaki Ariga, there is now a
      print(Z)
-#. How to negate a boolean, or to change the sign of a float inplace ? (★★★) 
+#. How to negate a boolean, or to change the sign of a float inplace? (★★★) 
   .. code-block:: python
@@ -676,7 +753,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider 2 sets of points P0,P1 describing lines (2d) and a point p, how to
-   compute distance from p to each line i (P0[i],P1[i]) ? (★★★) 
+   compute distance from p to each line i (P0[i],P1[i])? (★★★) 
   .. code-block:: python
@@ -695,7 +772,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider 2 sets of points P0,P1 describing lines (2d) and a set of points P,
-   how to compute distance from each point j (P[j]) to each line i (P0[i],P1[i]) ? (★★★) 
+   how to compute distance from each point j (P[j]) to each line i (P0[i],P1[i])? (★★★) 
   .. code-block:: python
@@ -742,7 +819,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider an array Z = [1,2,3,4,5,6,7,8,9,10,11,12,13,14], how to generate an
-   array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]] ? (★★★) 
+   array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]]? (★★★) 
   .. code-block:: python
@@ -762,7 +839,7 @@ Thanks to Michiaki Ariga, there is now a
      U, S, V = np.linalg.svd(Z) # Singular Value Decomposition
      rank = np.sum(S > 1e-10)
-#. How to find the most frequent value in an array ?
+#. How to find the most frequent value in an array?
   .. code-block:: python
@@ -803,7 +880,7 @@ Thanks to Michiaki Ariga, there is now a
      print(S)
 #. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1).
-   How to compute the sum of of the p matrix products at once ? (result has shape (n,1)) (★★★) 
+   How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) 
   .. code-block:: python
@@ -822,7 +899,7 @@ Thanks to Michiaki Ariga, there is now a
      # and 2 and 1, to remain with a (n,1) vector.
-#. Consider a 16x16 array, how to get the block-sum (block size is 4x4) ? (★★★) 
+#. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) 
   .. code-block:: python
@@ -834,7 +911,7 @@ Thanks to Michiaki Ariga, there is now a
                                             np.arange(0, Z.shape[1], k), axis=1)
-#. How to implement the Game of Life using numpy arrays ? (★★★) 
+#. How to implement the Game of Life using numpy arrays? (★★★) 
   .. code-block:: python
@@ -893,7 +970,7 @@ Thanks to Michiaki Ariga, there is now a
      print (cartesian(([1, 2, 3], [4, 5], [6, 7])))
-#. How to create a record array from a regular array ? (★★★) 
+#. How to create a record array from a regular array? (★★★) 
   .. code-block:: python
@@ -903,7 +980,7 @@ Thanks to Michiaki Ariga, there is now a
                                     names='col1, col2, col3',
                                     formats = 'S8, f8, i8')
-#. Comsider a large vector Z, compute Z to the power of 3 using 3 different
+#. Consider a large vector Z, compute Z to the power of 3 using 3 different
   methods (★★★)
   .. code-block:: python
@@ -924,7 +1001,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A
   that contain elements of each row of B regardless of the order of the elements
-   in B ? (★★★) 
+   in B? (★★★) 
   .. code-block:: python
@@ -951,7 +1028,6 @@ Thanks to Michiaki Ariga, there is now a
      print(U)
 #. Convert a vector of ints into a matrix binary representation (★★★) 
   .. code-block:: python
@@ -968,7 +1044,7 @@ Thanks to Michiaki Ariga, there is now a
      print(np.unpackbits(I[:, np.newaxis], axis=1))
-#. Given a two dimensional array, how to extract unique rows ? (★★★) 
+#. Given a two dimensional array, how to extract unique rows? (★★★) 
   .. code-block:: python
@@ -996,7 +1072,7 @@ Thanks to Michiaki Ariga, there is now a
 #. Considering a path described by two vectors (X,Y), how to sample it using
-   equidistant samples (★★★) ?
+   equidistant samples (★★★)?
   .. code-block:: python