added exercise for while loop in 004

Author: giumas

004_Loops.ipynb

@@ -48,11 +48,13 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Similarly to the [`if`](003_Conditional_Execution.ipynb#Applying-Conditions-with-if,-elif,-and-else) statement, a `for` loop requires that:\n",
+    "Similarly to the [`if`](003_Conditional_Execution.ipynb#Applying-Conditions-with-if,-elif,-and-else) statement, a `for` loop has several formatting requirements:\n",
     "\n",
-    "- There must be a subsequent element in the sequence; the condition following the `for` keyword must be `True`. \n",
-    "- You add a `:` at the end of the `for` condition.\n",
-    "- You indent all the lines of code that have to be executed in each iteration."
+    "- It begins with a `for` condition like `for <variable> in <sequence>` where:\n",
+    "  - `<sequence>` is the list over which to iterate.\n",
+    "  - `<variable>` is the name of a variable that will store the current value on each iteration. \n",
+    "- A `:` at the end of the `for` condition.\n",
+    "- The indentation of all the lines of code that have to be executed in each iteration."
    ]
   },
   {
@@ -414,6 +416,50 @@
     "The <button class='btn btn-default btn-xs'><i class=\"fa fa-stop\"></i></button> button in the Toolbar stops the execution of a **Code** cell. "
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "  "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "solution2": "hidden",
+    "solution2_first": true
+   },
+   "source": [
+    "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/test.png\">\n",
+    "\n",
+    "Add the code required to pop and then print all the values from the `sal_list`:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "solution2": "hidden"
+   },
+   "outputs": [],
+   "source": [
+    "sal_list = [32.1, 33.7, 35.0, 32.5, 31.9]  # water salinity in PSU\n",
+    "\n",
+    "while len(sal_list) > 0:\n",
+    "        \n",
+    "    removed_value = sal_list.pop()\n",
+    "    print(\"Removed element: \" + str(removed_value))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sal_list = [32.1, 33.7, 35.0, 32.5, 31.9]  # water salinity in PSU"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

005_Write_Your_Own_Functions.ipynb

@@ -495,7 +495,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Functions and their local variables"
+    "## Functions and Their Local Variables"
    ]
   },
   {