input: 
  def is_array_even(arr): 
      """Create an algorithm in Python to check whether an array has even or odd number of elements.
      >>> is_array_even([1, 2, 3, 4])
      True
      >>> is_array_even([1, 2, 3])
      False
      """
      return len(arr) % 2 == 0
  
output:     return len(arr) % 2 == 0