input: Write a function to calculate the average of a list of numbers in Python. The function should return the average of the numbers in the list. If the list is empty, the function should return 0.
  
  def avg_list(lst):
   if len(lst) == 0:
    return 0
   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, 40, 50])==30.0
  assert avg_list([-1, 0, 1])==0
  assert avg_list([7])==7
  assert avg_list([])==0
output: def avg_list(lst):
      if len(lst) == 0:
          return 0
      return sum(lst) / len(lst)