在 Pandas 数据框中为唯一行分配列值

Question

我有以下数据框：

AA          AB          AC                  AD              Col_1       Col_2     Col_3    
Northeast   Argentina   Northeast Argentina South America   Corrientes  Misiones        
Northern    Argentina   Northern  Argentina South America   Chaco       Formosa   Santiago Del 

我希望将其转换为：

AA          AB          AC                  AD              Col
Northeast   Argentina   Northeast Argentina South America   Corrientes
Northeast   Argentina   Northeast Argentina South America   Misiones        
Northern    Argentina   Northern  Argentina South America   Chaco
Northern    Argentina   Northern  Argentina South America   Formosa
Northern    Argentina   Northern  Argentina South America   Santiago Del 

我想保留前四列，但将其余列的每个值分配到单独的行中。是否有一种方法可以在不使用for循环的情况下完成此操作？

- user308827

Answer 1

你可以尝试这个方法：

df = df.melt(id_vars=['AA','AB','AC','AD']) 
df.dropna(inplace=True)
df.drop(columns='variable', inplace=True) 
df = df.sort_values('AA').reset_index(drop=True)
df.rename(columns={'value':'Col'}, inplace=True)

          AA         AB                   AC             AD           Col
0  Northeast  Argentina  Northeast Argentina  South America    Corrientes
1  Northeast  Argentina  Northeast Argentina  South America      Misiones
2   Northern  Argentina   Northern Argentina  South America         Chaco
3   Northern  Argentina   Northern Argentina  South America       Formosa
4   Northern  Argentina   Northern Argentina  South America  Santiago Del

- oppressionslayer

---

你可以通过不使用 inplace=True 来改进答案 - 参考这里。 - jezrael

不，我不是pandas的开发者，但是我经常看到这个观点并且同意它。我认为这更像是一个建议，还可以查看这个链接。 - jezrael

谢谢，这很有帮助。我感激你花时间帮助我成为更好的pandas专家。 - oppressionslayer

Answer 2

尝试使用：

。

df['Col'] = df[['Col_1', 'Col_2', 'Col_3']].values.tolist()
df = df.set_index(df.columns.drop('Col').tolist())['Col'].apply(pd.Series).stack().reset_index().rename(columns={0: 'Col'}).drop(['level_7', 'Col_1', 'Col_2', 'Col_3'], axis=1)
print(df)

输出：

          AA         AB                   AC             AD           Col
0  Northeast  Argentina  Northeast Argentina  South America    Corrientes
1  Northeast  Argentina  Northeast Argentina  South America      Misiones
2   Northern  Argentina   Northern Argentina  South America         Chaco
3   Northern  Argentina   Northern Argentina  South America       Formosa
4   Northern  Argentina   Northern Argentina  South America  Santiago Del

- U13-Forward