## Example 1: Manually raising a exception
def my_fun(a):
  try:
      if a == 20:
          raise ValueError("I don't want number 20")
      # or not specifying a specific exception like,
      # "raise Exception('my message')"
      print(f"{a} should be fine")
  except ValueError as v:
      print(v)

my_fun(20)  # I don't want number 20
my_fun(10)  # 10 should be fine