input: from typing import List
  
  def avg_list(lst: List[float]) -> float:
      """ Calculate the average of a list of numbers.
      >>> avg_list([1.0, 2.0, 3.0, 4.0])
      2.5
      >>> avg_list([5.5, 6.5, 7.5])
      6.5
      """
output:     return sum(lst) / len(lst) if lst else 0.0