input: Write a function to calculate the average of a list of numbers in Python.
  def avg_list(lst):
      sum = 0
      count = 0
      for i in lst:
          sum += i
          count += 1
      avg = sum / count
      return avg
  
  assert avg_list([1, 2, 3, 4, 5]) == 3.0
  assert avg_list([10, 20, 30]) == 20.0
  assert avg_list([1.5, 2.5, 3.5]) == 2.5
  assert avg_list([0, 0, 0, 0]) == 0.0
  assert avg_list([]) == 0
output: def avg_list(lst):
      if not lst:
          return 0
      sum = 0
      count = 0
      for i in lst:
          sum += i
          count += 1
      avg = sum / count
      return avg