擅长:python、mysql、java
<p>使用<a href="https://pandas.pydata.org/pandas-docs/version/0.23.4/generated/pandas.melt.html" rel="noreferrer">pd.melt</a>,如下所示:</p>
<pre><code>df['A'] = 'A'
df['B'] = 'B'
pd.melt(df, id_vars='Country', value_vars=['A', 'B']).sort_values('Country')
</code></pre>