title: How can I utilize OOP with this basic calculation script?
body: <p>I am trying to write a simple calculator to calculate how fast my battery will drain from 100% to 0% by taking a time and percentage for start and subtracting it from the finish time and percentage. </p>
  
  <p>I was able to make a quick and dirty script to accomplish this, but I am learning OOP, and I would like some feedback on how to improve my code and implement OOP for this task. I added in some verbose print statements to make it easier for me to remember what everything is when I run it, and I intend to wrap it up into a simple bash script or maybe implement tkinter for GUI. </p>
  
  <p>Any thoughts or suggestions will help! My main environment is python 3, but I added the error handling for those who run with python2 because it doesn't like a preceding 0 in the time number.</p>
  
  <pre><code>from datetime import timedelta
  
  # Getting inputs for time and percentage
  
  try:
      start_time = str(input('What is the starting time in 24 hour time? Format: HHMM &gt;&gt; '))
      start_time_hr = start_time[:2]
      start_time_min = start_time[2:]
  except SyntaxError:
      print('Try entering the time again without the preceding 0. \n')
      start_time = str(input('What is the starting time in 24 hour time? Format: HHMM &gt;&gt; '))
      start_time_hr = start_time[0]
      start_time_min = start_time[1:]
  
  start_perc = int(input('What is the starting battery percentage? &gt;&gt; '))
  
  try:
      end_time = str(input('What is the finish time in 24 hour time? Format: HHMM &gt;&gt; '))
      end_time_hr = end_time[:2]
      end_time_min = end_time[2:]
  except SyntaxError:
      print('Try entering the time again without the preceding 0. \n')
      end_time = str(input('What is the finish time in 24 hour time? Format: HHMM &gt;&gt; '))
      end_time_hr = end_time[0]
      end_time_min = end_time[1:]
  
  end_perc = int(input('What is the ending battery percentage? &gt;&gt; '))
  
  # Turning numbers into times for calculation
  
  start = timedelta(hours=int(start_time_hr), minutes=int(start_time_min))
  end = timedelta(hours=int(end_time_hr), minutes=int(end_time_min))
  
  # Calculating and printing the results
  
  perc_difference = float(-(end_perc - start_perc))
  time_difference = end - start
  time_difference_minute = time_difference.total_seconds() / 60
  discharge = (100.0 * time_difference_minute / perc_difference) / 60
  
  print()
  print()
  print('*****')
  print('Percentage Difference = ' + str(perc_difference))
  print('Minutes Passed = ' + str(time_difference.total_seconds() / 60))
  print('100% to 0% in ~' + str(round(discharge, 2)) + ' hours.')
  print('*****')
  print()
  print()
  print()
  </code></pre>