input: Write a function to count the number of even numbers in a given list. If the list is empty, return 0.
  
  assert countEvenNum([1, 2, 3, 4, 5]) == 2
  assert countEvenNum([2, 4, 6, 8]) == 4
  assert countEvenNum([1, 3, 5, 7]) == 0
  assert countEvenNum([]) == 0
output: def countEvenNum(lst):
      return sum(1 for x in lst if x % 2 == 0)