<p>熊猫有pd合并[<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.merge.html]" rel="nofollow noreferrer">https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.merge.html]</a>函数,默认情况下使用内部联接。如果两个数据帧中要合并的键不同,内部联接基本上只接受在<code>on</code>或<code>left_on</code>和<code>right_on</code>中指定的两个键中都存在的值。在</p>
<p>由于需要添加<code>CODE</code>值,因此可以使用以下代码行:</p>
<p><code>pd.merge(left=df, right=df2[['COUNTRY', 'CODE']], left_on='name', right_on='COUNTRY', how='left')</code></p>
<p>这将产生以下输出:</p>
<pre><code> name Longitude Latitude continent COUNTRY CODE
0 Aruba -69.982677 12.520880 North America NaN NaN
1 Afghanistan 66.004734 33.835231 Asia Afghanistan AFG
2 Angola 17.537368 -12.293361 Africa NaN NaN
3 Anguilla -63.064989 18.223959 North America NaN NaN
4 Albania 20.049834 41.142450 Europe Albania ALB
</code></pre>
<p>以下也给出了相同的结果:</p>
<p><code>new_df = pd.merge(left=df1[['COUNTRY', 'CODE']], right=df, left_on='COUNTRY', right_on='name', how='right')</code></p>
^{pr2}$