diff --git a/module3.ipynb b/module3.ipynb
index a1227d8..bd78239 100644
--- a/module3.ipynb
+++ b/module3.ipynb
@@ -492,16 +492,22 @@
     "log = \"July 31 07:51:48 mycomputer bad_process[12345]: ERROR Performing package upgrade\"\n",
     "regex = r\"\\[(\\d+)\\]\"\n",
     "result = re.search(regex, log)\n",
+    "# This will match any string with a number enclosed in square brackets like [12345] or [67890] etc. \n",
+    "# But if the string does not have such a pattern, it returns None. \n",
+    "# We'll use this function later to extract PID from our log strings.\n",
     "result = re.search(regex, \"A completely different string that also has numbers [34567]\")\n",
     "result = re.search(regex, \"99 elephants in a [cage]\")\n",
     "def extract_pid(log_line):\n",
+    "    # This function takes as input a log line (string) and returns the number within square brackets if such a pattern exists in the string\n",
     "    regex = r\"\\[(\\d+)\\]\"\n",
     "    result = re.search(regex, log_line)\n",
-    "    if result is None:\n",
-    "        return \"\"\n",
-    "    return result[1]\n",
+    "    if result is None: \n",
+    "        return \"No PID found\" # If no match found, return this message.\n",
+    "    return result[1] # The result[1] will be the number within square brackets in string format.  \n",
     "print(extract_pid(log))\n",
-    "print(extract_pid(\"99 elephants in a [cage]\"))\n",
+    "# It prints '12345' as there is a pattern [12345] in the given log line\n",
+    "print(extract_pid(\"99 elephants in a [cage]\")) \n",
+    "# It prints 'No PID found' as there are no numbers within square brackets in this string.\n",
     "# Output:\n",
     "# 12345"
    ]
diff --git a/module4.ipynb b/module4.ipynb
index 709d82c..e959f55 100644
--- a/module4.ipynb
+++ b/module4.ipynb
@@ -1,11 +1,63 @@
 {
  "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Reading data interactively"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
    "metadata": {},
    "outputs": [],
-   "source": []
+   "source": [
+    "cat hello.py\n",
+    "#!/usr/bin/env python3\n",
+    "\n",
+    "name = input(\"Please enter your name: \")\n",
+    "print(\"Hello, \" + name)\n",
+    "\n",
+    "# ./hello.py \n",
+    "# Please enter your name: Roger\n",
+    "# #Output will be Hello, Roger"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# defining a function called 'to_seconds' which takes hours, minutes and seconds as\n",
+    "# inputs and returns their total equivalent in seconds by multiplying each with its\n",
+    "# corresponding factor (3600 for hours, 60 for minutes) and then summing them up.\n",
+    "def to_seconds(hours, minutes, seconds):\n",
+    "    return hours*3600+minutes*60+seconds\n",
+    "\n",
+    "# Print a welcome message to the user\n",
+    "print(\"Welcome to this time converter\")\n",
+    "\n",
+    "# set 'cont' variable to \"y\" initially for entering into while loop.\n",
+    "cont = \"y\"\n",
+    "\n",
+    "# while condition is true (user wants to continue), keep asking the\n",
+    "# number of hours, minutes and seconds from the user and print their total equivalent\n",
+    "# in seconds by calling 'to_seconds' function. Ask if they want to do another conversion.\n",
+    "# If not, break the loop.\n",
+    "while(cont.lower() == \"y\"):\n",
+    "    hours = int(input(\"Enter the number of hours: \"))\n",
+    "    minutes = int(input(\"Enter the number of minutes: \"))\n",
+    "    seconds = int(input(\"Enter the number of seconds: \"))\n",
+    "\n",
+    "    print(\"That's {} seconds\".format(to_seconds(hours, minutes, seconds)))\n",
+    "    print()\n",
+    "    cont = input(\"Do you want to do another conversion? [y to continue] \")\n",
+    "    \n",
+    "# print a goodbye message when user decides to stop the program.\n",
+    "print(\"Goodbye!\")\n"
+   ]
   }
  ],
  "metadata": {