擅长:python、mysql、java
<p>如果您不想使用逐行读卡器和defaultdict,那么这是通过<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.pivot_table.html" rel="nofollow noreferrer">pandas.pivot_table</a>得到的一行高级答案。你知道吗</p>
<pre><code>import pandas as pd
df = pd.DataFrame([['a', 'b', 1], ['a', 'b', 3], ['b', 'a', 2], ['b', 'c', 4],
['c', 'a', 5], ['c', 'b', 5], ['c', 'b', 3], ['c', 'a', 4]],
columns=['out_gate', 'in_gate', 'num_connection'])
pd.pivot_table(df, index='out_gate', columns='in_gate', values='num_connection', aggfunc='sum').fillna(0)
</code></pre>