--- a/PythonForJsProgrammers.html	Tue Jun 10 23:52:50 2008 -0700
+++ b/PythonForJsProgrammers.html	Tue Jun 10 23:56:18 2008 -0700
@@ -73,11 +73,14 @@
 else:
     doOtherThing()
 </pre>
-<p>Also note that Python doesn't use semicolons, which is yet another
-language feature that reduces the cognitive burden on the programmer.
-Indeed, many of the language features covered below were designed with
-a very careful eye towards readability, reducing cognitive load, and
-making the process of programming <a class="reference" href="http://xkcd.com/353/">as enjoyable as possible</a>.</p>
+<p>Python is technically like JavaScript in that semicolons are optional,
+but its community prescribes the opposite convention: that is,
+semicolons should <em>never</em> be used to delimit statements unless
+absolutely necessary.  This is yet another decision that reduces the
+cognitive burden on the programmer; indeed, many of the language
+features covered below were designed with a very careful eye towards
+readability, reducing cognitive load, and making the process of
+programming <a class="reference" href="http://xkcd.com/353/">as enjoyable as possible</a>.</p>
 </div>
 <div class="section">
 <h1><a id="the-interactive-shell" name="the-interactive-shell">The Interactive Shell</a></h1>
@@ -120,16 +123,20 @@
 </blockquote>
 <p>If there's a function you're interested in learning more about, you
 can look at the built-in documentation metadata associated with the
-object--known as the <cite>docstring</cite>--by querying the object's <tt class="docutils literal"><span class="pre">__doc__</span></tt>
-attribute.  For instance, here's how to get help on the string
-object's <tt class="docutils literal"><span class="pre">join()</span></tt> method:</p>
+object--known as the <cite>docstring</cite>--by calling the built-in <tt class="docutils literal"><span class="pre">help()</span></tt>
+function on the object.  For instance, here's how to get help on the
+string object's <tt class="docutils literal"><span class="pre">join()</span></tt> method:</p>
 <blockquote>
 <pre class="doctest-block">
-&gt;&gt;&gt; print &quot;a string&quot;.join.__doc__
-S.join(sequence) -&gt; string
+&gt;&gt;&gt; help(&quot;a string&quot;.join)
+Help on built-in function join:
 &lt;BLANKLINE&gt;
-Return a string which is the concatenation of the strings in the
-sequence.  The separator between elements is S.
+join(...)
+    S.join(sequence) -&gt; string
+&lt;BLANKLINE&gt;
+    Return a string which is the concatenation of the strings in the
+    sequence.  The separator between elements is S.
+&lt;BLANKLINE&gt;
 </pre>
 </blockquote>
 <p>This makes it easy and fun to explore the language and its environs.</p>
@@ -260,15 +267,7 @@
 AttributeError: 'str' object has no attribute 'foo'
 </pre>
 </blockquote>
-<p>In most cases, this is for the best, as it makes debugging easier.  If
-you really need to find out if an object has a particular attribute,
-however, you can use the <tt class="docutils literal"><span class="pre">hasattr()</span></tt> function:</p>
-<blockquote>
-<pre class="doctest-block">
-&gt;&gt;&gt; hasattr(&quot;a string&quot;, &quot;foo&quot;)
-False
-</pre>
-</blockquote>
+<p>In most cases, this is for the best, as it makes debugging easier.</p>
 <p>Python also has an analog to JavaScript's <tt class="docutils literal"><span class="pre">null</span></tt>: it's called
 <tt class="docutils literal"><span class="pre">None</span></tt>.</p>
 </div>
@@ -343,7 +342,7 @@
 ...     pass
 </pre>
 </blockquote>
-<p>As mentioned earlier, this string is called the docstring, and is
+<p>As mentioned earlier, this string is called the docstring; it's
 actually attached to the function object as its <tt class="docutils literal"><span class="pre">__doc__</span></tt> attribute.
 Creating docstrings for your functions not only helps document your
 code, but also makes it easier for Python users to interactively
@@ -401,8 +400,8 @@
 there
 </pre>
 </blockquote>
-<p>Strings are just sequences of characters, so they can be used
-similarly:</p>
+<p>Strings are just sequences of single-character strings, so they can be
+used similarly:</p>
 <blockquote>
 <pre class="doctest-block">
 &gt;&gt;&gt; for c in &quot;boof&quot;:
@@ -535,12 +534,29 @@
 'Hello bob, I need 5 dollars.'
 </pre>
 </blockquote>
+<p>Keys for dictionaries can actually be any immutable type; this means
+that, for instance, tuples can be used as keys:</p>
+<blockquote>
+<pre class="doctest-block">
+&gt;&gt;&gt; a = {(1,2) : 1}
+</pre>
+</blockquote>
+<p>But lists can't:</p>
+<blockquote>
+<pre class="doctest-block">
+&gt;&gt;&gt; b = {[1,2] : 1}
+Traceback (most recent call last):
+...
+TypeError: list objects are unhashable
+</pre>
+</blockquote>
 <p>Python dictionaries generally aren't used to create arbitrary objects
 like they are in Javascript; they don't have prototypes, nor do they
 have meta-methods.  Instead, classes are used to do that sort of
 thing.  In some ways, this is unfortunate, since the simplicity of
 conflating objects with dictionaries, as JavaScript and Lua do, makes
-understanding and using them easier.</p>
+understanding and using them easier.  But in exchange, dictionaries do
+come pre-packaged with a bevy of <a class="reference" href="http://docs.python.org/lib/typesmapping.html">useful methods</a>.</p>
 </div>
 <div class="section">
 <h1><a id="classes" name="classes">Classes</a></h1>
@@ -869,6 +885,11 @@
 the <a class="reference" href="http://mail.python.org/mailman/listinfo/tutor">tutor mailing list</a>, and a <a class="reference" href="http://wiki.python.org/moin/LocalUserGroups">local user group</a> if your area has
 one.</p>
 </div>
+<div class="section">
+<h1><a id="feedback" name="feedback">Feedback</a></h1>
+<p>If you have any suggestions or comments regarding this tutorial,
+please feel free to post them to <a class="reference" href="http://www.toolness.com/wp/?p=45">this blog post</a>.  Thanks!</p>
+</div>
 </div>
 </body>
 </html>