notebook 3: minor changes to first example of file reading

notebooks/03_reading_writing_files.ipynb

@@ -199,11 +199,53 @@
     "\n",
     "Once there are no more lines to read, `.readline()` **returns an empty string (`\"\"`)**. This is how we know that the end of the file was reached.\n",
     "\n",
-    "<img src=\"img/file_pointer5.png\" alt=\"a file pointer at the end of the file\" style=\"height:200px;\" />\n",
+    "<img src=\"img/file_pointer5.png\" alt=\"a file pointer at the end of the file\" style=\"height:200px;\" />\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "<br>\n",
+    "<br>\n",
+    "\n",
+    "**Let's see an example with actual code:**\n",
     "\n",
+    "Here we are going to read the file `data/fresh_fruits.txt`, which has the following content:\n",
+    "\n",
+    "```\n",
+    "passionfruit\n",
+    "oranges\n",
+    "apples\n",
+    "grapefruit (whole and segments)\n",
+    "pointed sticks\n",
+    "```\n",
+    "\n",
+    "<br>\n",
+    "\n",
+    "* Open the file, and read a single line from it:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "with open(\"data/fresh_fruits.txt\" , mode=\"r\") as reading_handle:\n",
+    "    \n",
+    "    # Read and print the first line in the file.\n",
+    "    line = reading_handle.readline()  # Reads a single line from the file.\n",
+    "    print(\"line 1:\", line)            # Print the line to the screen.\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
     "<br>\n",
     "\n",
-    "**Let's see an example with actual code:**"
+    "* Open the file, and read all of its content, line by line:"
    ]
   },
   {