擅长:python、mysql、java
<p>你可以做:</p>
<pre><code>result = pd.concat([A.melt(id_vars='Country', var_name='Year', value_name='Population'),
B.melt(id_vars='Country', var_name='Year', value_name='Population')]).dropna()
print(pd.crosstab(index=result.Country, columns=result.Year, values=result.Population, aggfunc='mean'))
</code></pre>
<p><strong>输出</strong></p>
<pre><code>Year 2014 2015 2016 2017 2018 2019
Country
China NaN NaN 1100.0 1200.0 1300.0 NaN
India 780.0 810.0 810.0 NaN 1100.0 1300.0
Nigeria 90.0 100.0 105.0 NaN NaN 110.0
UK 58.0 60.0 NaN 63.0 65.0 68.0
USA 319.0 321.0 323.5 325.0 328.0 330.0
</code></pre>