input: 
  from typing import List
  
  def countEvenNum(list: List[int]) -> int:
      """ 
      This function counts the number of even numbers in a given list of integers.
      >>> countEvenNum([1, 2, 3, 4, 5])
      2
      >>> countEvenNum([10, 15, 16, 21, 27])
      2
      """
      return len([x for x in list if x % 2 == 0])
  
output:     count = 0
      for num in list:
          if num % 2 == 0:
              count += 1
      return count