擅长:python、mysql、java
<p>这应该做到:</p>
<pre><code>def averageGrades(diction):
avgDict = {}
for k, v in diction.items():
# v is the list of grades for student k
avgDict[k] = sum(v)/ float(len(v))
return avgDict
^^^^^
</code></pre>
<p>缩进很重要。在</p>
<p>函数在第一个循环处停止,因为<code>return</code>语句是在<code>for</code>语句结束之前编写的</p>