<p>您还可以根据获得的索引和<code>reindex</code>创建笛卡尔乘积索引列表:</p>
<pre><code>out = df.groupby(['Group', 'Cat']).describe()
idx = pd.MultiIndex.from_product((out.index.levels[0],out.index.levels[1]))
out = out.reindex(idx,fill_value=0)
</code></pre>
<hr/>
<pre><code> Value
count mean std min 25% 50% 75% max
Group1 Cat 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat1 1.0 1230.0 NaN 1230.0 1230.0 1230.0 1230.0 1230.0
Cat2 1.0 4019.0 NaN 4019.0 4019.0 4019.0 4019.0 4019.0
Cat3 1.0 9491.0 NaN 9491.0 9491.0 9491.0 9491.0 9491.0
Cat4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Group2 Cat 1.0 1923.0 NaN 1923.0 1923.0 1923.0 1923.0 1923.0
Cat1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat4 1.0 9588.0 NaN 9588.0 9588.0 9588.0 9588.0 9588.0
Cat5 1.0 6402.0 NaN 6402.0 6402.0 6402.0 6402.0 6402.0
Cat7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Group3 Cat 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Cat1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
....................................
...............................
</code></pre>