擅长:python、mysql、java
<p>在<code>groupby</code>上运行<code>sum</code>,然后<code>reset_index()</code>将其展平。像这样:</p>
<pre><code>df.groupby(['YEAR', 'REGION']).sum().reset_index()
# YEAR REGION POWER
# 0 2009 East 19.30
# 1 2009 West 3.43
# 2 2010 North 19.40
# 3 2010 West 14.90
# 4 2011 East 16.66
</code></pre>