擅长:python、mysql、java
<p>或者干脆<code>replace</code>:</p>
<pre><code>trainTestJoin['col1'] = trainTestJoin['col1'].replace('NA',np.nan)
</code></pre>
<p>然后简单地说:</p>
<pre><code>trainTestJoin['col1'] = trainTestJoin['col1'].fillna(trainTestJoin.groupby('col2')['col1'].transform('mean'))
</code></pre>
<p>现在(毕竟):</p>
<pre><code>print(trainTestJoin)
</code></pre>
<p>是预期的产量</p>