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