ipynb

Author: katyhuff

01-basics.html

@@ -66,7 +66,6 @@ <h2>Key Points</h2>
 <ul>
 <li>Tests compare that the result observed from running code is the same as what was expected ahead of time.</li>
 <li>Tests should be written at the same time as the code they are testing is written.</li>
-<li>The person best suited to write a test is the author of the original code.</li>
 <li>Assertions and exceptions are like alarm systems embedded in the software, guarding against exceptional bahavior.</li>
 <li>Unit tests try to test the smallest pieces of code possible, usually functions and methods.</li>
 <li>Integration tests make sure that code units work together properly.</li>

01-basics.md

@@ -55,7 +55,6 @@ software work together as expected.
 > 
 > - Tests compare that the result observed from running code is the same as what was expected ahead of time.
 > - Tests should be written at the same time as the code they are testing is written.
-> - The person best suited to write a test is the author of the original code.
 > - Assertions and exceptions are like alarm systems embedded in the software, guarding against exceptional bahavior.
 > - Unit tests try to test the smallest pieces of code possible, usually functions and methods.
 > - Integration tests make sure that code units work together properly.

02-assertions.html

@@ -52,20 +52,22 @@ <h2><span class="glyphicon glyphicon-certificate"></span>Learning Objectives</h2
     <span class="kw">assert</span> <span class="dt">len</span>(num_list) != <span class="dv">0</span>
     <span class="kw">return</span> <span class="dt">sum</span>(num_list)/<span class="dt">len</span>(num_list)</code></pre>
 <p>The advantage of assertions is their ease of use. They are rarely more than one line of code. The disadvantage is that assertions halt execution indiscriminately and the helpfulness of the resulting error message is usually quite limited.</p>
+<p>Also, input checking may require decending a rabbit hole of exceptional cases. What happens when the input provided to the mean function is a string, rather than a list of numbers?</p>
 <section class="challenge panel panel-success">
 <div class="panel-heading">
-<h2><span class="glyphicon glyphicon-pencil"></span>Insert an Assertion</h2>
+<h2><span class="glyphicon glyphicon-pencil"></span>Challenge Insert an Assertion</h2>
 </div>
 <div class="panel-body">
 <ol style="list-style-type: decimal">
-<li>Create a new IPython Notebook</li>
+<li>Open an IPython Notebook</li>
 <li>Create the following function:</li>
 </ol>
 <pre class="sourceCode python"><code class="sourceCode python"><span class="kw">def</span> mean(num_list):
   <span class="kw">return</span> <span class="dt">sum</span>(num_list)/<span class="dt">len</span>(num_list)</code></pre>
 <ol start="3" style="list-style-type: decimal">
-<li>In the function, insert an assertion that checks whether the list is made of numbers.</li>
+<li>In the function, insert an assertion that checks whether the input is actually a list.</li>
 </ol>
+<p>Hint: Use the <a href="https://docs.python.org/2/library/functions.html#isinstance">isinstance function</a>.</p>
 </div>
 </section>
 <p>Assertions are also helpful for catching abnormal behaviors, such as those that arise with floating point arithmetic.</p>

02-assertions.ipynb

@@ -113,7 +113,7 @@
    },
    "outputs": [],
    "source": [
-    "mean([\"nonempty\",\"but\",\"not\", \"numbers\"])"
+    "mean(\"nonempty-nonlist\")"
    ]
   },
   {
@@ -122,7 +122,7 @@
    "source": [
     "____\n",
     "### Challenge: Insert an Assertion\n",
-    "In the following code, insert an assertion that checks whether the list is made of numbers."
+    "In the following code, use the [isinstance function](https://docs.python.org/2/library/functions.html#isinstance) to insert an assertion that checks whether the input is a list."
    ]
   },
   {
@@ -136,7 +136,7 @@
     "def mean(num_list):\n",
     "    assert len(num_list) != 0, \"the input is empty\"\n",
     "    # insert your assertion here\n",
-    "  return sum(num_list)/len(num_list)"
+    "    return sum(num_list)/len(num_list)"
    ]
   },
   {
@@ -160,7 +160,7 @@
    "outputs": [],
    "source": [
     "# Does this cause it to halt with a type message?\n",
-    "mean([\"test\"])"
+    "mean(\"test\")"
    ]
   },
   {
@@ -200,9 +200,9 @@
    "outputs": [],
    "source": [
     "from mynum import a\n",
-    "# greater than 2 assertion here\n",
-    "# 2 decimal places assertion here\n",
-    "# 0.003 assertion here"
+    "# a is greater than 2 assertion here\n",
+    "# a is within 2 decimal places of 2 assertion here\n",
+    "# a is within 0.003 of 2 assertion here"
    ]
   },
   {

02-assertions.md

@@ -44,19 +44,26 @@ line of code. The disadvantage is that assertions halt execution
 indiscriminately and the helpfulness of the resulting error message is usually
 quite limited. 
 
+Also, input checking may require decending a rabbit hole of exceptional cases. 
+What happens when the input provided to the mean function is a string, rather 
+than a list of numbers?
 
-> ## Insert an Assertion {.challenge}
+
+> ## Challenge Insert an Assertion {.challenge}
+>
 >
-> 1. Create a new IPython Notebook
+> 1. Open an IPython Notebook
 > 2. Create the following function:
 >
 > ~~~ {.python}
 > def mean(num_list):
 >   return sum(num_list)/len(num_list)
 > ~~~
 >
-> 3. In the function, insert an assertion that checks whether the list is 
-> made of numbers.
+> 3. In the function, insert an assertion that checks whether the input is 
+> actually a list.
+> 
+> Hint: Use the [isinstance function](https://docs.python.org/2/library/functions.html#isinstance). 
 >