擅长:python、mysql、java
<p><strong>更新:</strong></p>
<pre><code>In [43]: df.groupby(['CustomerID', pd.Grouper(key='InvoiceDate', freq='QS')]) \
.size() \
.reset_index(name='Count')
Out[43]:
CustomerID InvoiceDate Count
0 12877.0 2011-04-01 1
1 13654.0 2011-07-01 1
2 14841.0 2010-10-01 1
3 15073.0 2011-04-01 1
4 19543.0 2011-10-01 1
</code></pre>
<hr/>
<p>这就是你想要的吗?你知道吗</p>
<pre><code>In [39]: df.groupby(pd.Grouper(key='InvoiceDate', freq='QS')).count()
Out[39]:
CustomerID
InvoiceDate
2010-10-01 1
2011-01-01 0
2011-04-01 2
2011-07-01 1
2011-10-01 1
</code></pre>