擅长:python、mysql、java
<p>假设只需要<code>product</code>个值<a href="https://docs.python.org/3/library/itertools.html#itertools.product" rel="nofollow noreferrer">^{<cd2>}</a>比<code>pandas</code>函数的开销小得多:</p>
<pre><code>from itertools import product
import pandas as pd
df = pd.DataFrame({'Name': ['Joe', 'Ellen', 'Zach'],
'Department': ['A', 'A', 'A']})
</code></pre>
<p>从<a href="https://pandas.pydata.org/docs/reference/api/pandas.Series.unique.html" rel="nofollow noreferrer">^{<cd4>}</a>名称计算新数据帧:</p>
<pre><code>df = pd.DataFrame(product(df['Name'].unique(),
['A', 'B', 'C', 'D']),
columns=df.columns)
</code></pre>
<p><code>df</code>:</p>
<pre><code> Name Department
0 Joe A
1 Joe B
2 Joe C
3 Joe D
4 Ellen A
5 Ellen B
6 Ellen C
7 Ellen D
8 Zach A
9 Zach B
10 Zach C
11 Zach D
</code></pre>