count vowels

vow = ['a', 'A', 'e',
          'E', 'i', 'I',
          'o', 'O', 'U',
          'u', 'Y', 'y']

def vowels(str):
  
  global vow
  string = list(str)
  count = 0
  
  for i in range(len(string)):
    
    if string[i] in vow:
      
      count += 1
  return count