started 005

Author: nbgitpuller

Diff for: 005_Write_Your_Own_Functions.ipynb

@@ -21,13 +21,89 @@
     "# Write Your Own Functions"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "In the past notebooks, we have met (and used) several of the many functions that are shipped with Python."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "It is now time to empower you with the capability to create your own function. But what is a function?"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
     "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/key.png\">\n",
     "\n",
-    "A key concept."
+    "A **function** is a named sequence of statements."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Function declaration"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "If you want to create your own function:\n",
+    "\n",
+    "1. You first need to think at a meaningful name to give to it. \n",
+    "2. You put the selected name after the `def` keyword, followed by curved parentheses and ending with a `:`.\n",
+    "3. Since the following line, you indent the body of the function (that is, the code that has to be executed)."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def print_temp_list():\n",
+    "    temp_list = [23.0, 19.2, 18.5, 21.3, 20.4]\n",
+    "    print(temp_list)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "When you execute the above **Code** cell, nothing is printed. No worries, this is correct! We have **only** declared the function. We can now call the declared function:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[23.0, 19.2, 18.5, 21.3, 20.4]\n"
+     ]
+    }
+   ],
+   "source": [
+    "print_temp_list()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/key.png\">\n",
+    "\n",
+    "A function has to be first declared using the `def` keyword, than it can be called (i.e., executed) multiple times."
    ]
   },
   {
@@ -40,32 +116,47 @@
   {
    "cell_type": "markdown",
    "metadata": {
-    "solution2": "hidden",
+    "solution2": "shown",
     "solution2_first": true
    },
    "source": [
     "<img align=\"left\" width=\"6%\" style=\"padding-right:10px;\" src=\"images/test.png\">\n",
     "\n",
-    "Write code that ..."
+    "Modify the code to call a function that prints the number of elements in the `sal_list`."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 4,
    "metadata": {
-    "solution2": "hidden"
+    "solution2": "shown"
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Nr. of elements: 7\n"
+     ]
+    }
+   ],
    "source": [
-    "x = 0"
+    "def print_len_sal_list():\n",
+    "    sal_list = [32.6, 33.3, 34.8, 32.4, 34.3, 33.7, 32.3]  # water salinity in PSU\n",
+    "    len_sal_list = len(sal_list)\n",
+    "    print(\"Nr. of elements: \" + str(len_sal_list))\n",
+    "    \n",
+    "print_len_sal_list()"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [],
-   "source": []
+   "source": [
+    "sal_list = [32.6, 33.3, 34.8, 32.4, 34.3, 33.7, 32.3]"
+   ]
   },
   {
    "cell_type": "markdown",