input: Write a function to calculate the average of a list of numbers in Python. If the given list is empty, return 0.
  def avg_list(lst):
   if not lst:
    return 0
   sum = 0
   for i in lst:
    sum += i
   avg = sum / len(lst)
   return avg
  assert avg_list([1, 2, 3, 4, 5]) == 3.0
  assert avg_list([10, 20, 30]) == 20.0
  assert avg_list([9, 5, 8, 7, 3]) == 6.4
  assert avg_list([11, 12, 9]) == 10.666666666666666
  assert avg_list([]) == 0
output: def avg_list(lst):
   if not lst:
    return 0
   sum = 0
   for i in lst:
    sum += i
   avg = sum / len(lst)
   return avg