擅长:python、mysql、java
<p>下面是你想要的</p>
<p>使用groupby创建Cars数据帧</p>
<pre><code>CarsDF = pd.DataFrame(df.groupby(['Car','CarModel']).Car.count())
CarsDF.columns=['v']
CarsDF = CarsDF.reset_index().drop('v', axis=1)
CarsDF.index.name='CarId'
CarsDF
</code></pre>
<p>然后使用merge添加CarId</p>
<pre><code>PersonDF = df.merge(CarsDF.reset_index())[['PersonName','PersonAge','CarId']]
</code></pre>