擅长:python、mysql、java
<p>更快的矢量化方法是使用<code>np.repeat</code>和<code>np.concatenate</code></p>
<pre><code>In [2272]: pd.DataFrame({'ID': df1['ID'].values.repeat(df1['Key'].str.len()),
...: 'Key': np.concatenate(df1['Key']),
...: 'Value': np.concatenate(df1['Value'])})
Out[2272]:
ID Key Value
0 ID1 key1a value1a
1 ID1 key1b value1b
2 ID1 key1c value1c
3 ID2 key2a value2a
4 ID2 key2b value2b
5 ID2 key2c value2c
</code></pre>
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<p><strong>计时</strong></p>
^{pr2}$