擅长:python、mysql、java
<p>你可以把事情缩短一点:</p>
<pre><code>def count_vowels_recursive(sentence):
# this base case is needed to stop the recursion
if not sentence:
return 0
# otherwise, sentence[0] will raise an exception for the empty string
return (sentence[0] in "aeiou") + count_vowels_recursive(sentence[1:])
# the boolean expression `sentence[0] in "aeiou"` is cast to an int for the addition
</code></pre>