week3-journal.py

# count from a postive num descinding dwon to 0.
def countdown(n):
     # base case
     if n <= 0:
          print('Blastoff!')
     else:
          print(n)
          countdown(n-1)

# count from a negative num ascending up to 0.
def countup(n):
     # base case
     if -n <= 0:
          print('Blastoff!')
     else:
          print(n)
          countup(n+1)

# handling user input
def handle_user_input(str_input):
  try:
    # trnsforming the input string into number
    num = int(str_input)
    """
    if the user did not enter a valid number we argoing to face a RuntimeError

    so everything is fine but the int() function can not work if we did not enter a valid number

    we can handle this error by handling the Exception and show and appropriate error message that prevent our program from crashing
    
    """
  except:
    # handling if the user did not enter a valid number without breaking the program
    return print("Error: please Enter a valid number \n")

  # if num is positive
  if num > 0:
    countdown(num)
  # if num is negative
  elif num < 0:
    countup(num)
  # if num is 0
  else:
    print(num,  "\n")


if __name__ == "__main__":
  # continue the program until you press ctrl + c to close the program
  while True:
    user_input = input("enter a number : \n")
    handle_user_input(user_input)
    print("___________________________________________________________\n")