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<p>在使用多个数据帧时,我在使用<code>groupby</code>和<code>aggregation</code>时遇到问题。我试图从两个不同的数据帧计算<code>num_maint_over_$90</code>。在</p>
<pre><code>cars_dict = {"ABC123": ["Ford", "Compact_Car"], "XYZ148": ["Chevy", "Truck"], "ASX133": ["Ford", "Truck"], "ADS111": ["Porsche", "Sports_Car"], "SSC119": ["Toyota", "Compact_Car"]}
cars = pd.DataFrame.from_dict(cars_dict, orient = 'index')
cars.columns = ["Manufacturer", "Type"]
cars.index.rename("License_Plate", inplace = True)
maintenance_dict = {"License_Plate": ["ABC123", "ABC123", "ABC123", "XYZ148", "ASX133", "ASX133", "ADS111", "ADS111", "SSC119"], "Cost": [60, 100, 200, 150, 40, 199, 33, 99, 0]}
maintenance_records = pd.DataFrame.from_dict(maintenance_dict)
maintenance_records.index.rename("order_num", inplace = True)
</code></pre>
<p><strong>*汽车:</strong></p>
^{pr2}$
<p><strong>*维护记录:</strong></p>
<pre><code> Cost License_Plate
order_num
0 60 ABC123
1 100 ABC123
2 200 ABC123
3 150 XYZ148
4 40 ASX133
5 199 ASX133
6 33 ADS111
7 99 ADS111
8 0 SSC119
</code></pre>
<p><strong>*所需数据框:</strong></p>
<pre><code>Type num_maint_over_$90
Compact_Car 2
Sports_Car 1
Truck 2
</code></pre>
<p>我试过使用<code>groupby</code>、<code>apply()</code>、和{<cd6>}。在</p>