擅长:python、mysql、java
<p>我认为您可以通过使用<code>df2</code>创建的<code>Series</code>使用<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.insert.html" rel="noreferrer">^{<cd1>}</a>和<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.map.html" rel="noreferrer">^{<cd2>}</a>(如果<code>df2</code>中的<code>MODEL</code>列中缺少get<code>NaN</code>中的某个值):</p>
<pre><code>df1.insert(2, 'MAKE', df1['MODEL'].map(df2.set_index('MODEL')['MAKE']))
print (df1)
ID MODEL MAKE REQUESTS ORDERS
0 1 Golf Volkswagen 123 4
1 2 Passat NaN 34 5
2 3 Model 3 Tesla 500 8
3 4 M3 BMW 5 0
</code></pre>