#以下方法可计算字符串中元音字母（‘a’, ‘e’, ‘i’, ‘o’, ‘u’）的数目。

import re
def count_vowels(str):
    return len(len(re.findall(r [aeiou] , str, re.IGNORECASE)))
count_vowels( foobar ) # 3
count_vowels( gym ) # 0