将数据框的多列值复制到另一个数据框的一列中

Question

   ID  a1 a2 b1 b2 .
    1   
    2
    3
    4
    ... 
    300

我想创建一个新的数据框合并列 a1 a2 和 b1，b2。目的是获得这样的东西：

     ID  a  b 
     1   
     2
     3
     4
     ... 
     600

其中 a 基本上由两列 a1、a2 依次给出。有什么建议么？

Answer 1

实际上它确实有效，但我想知道是否有更快的解决方案。这是代码：df1 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df2 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df3 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df4 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df5 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df6 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df7 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df8 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df9 = pd.DataFrame(columns=['CNTR_CODE', 'Risk_damage', 'pot_tot_loss','annual_tot_loss'])df1[["CNTR_CODE", 'Risk_damage', 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'Risk_damage0','pot_tot_loss00', 'annual_tot_loss00']]df2[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss01','annual_tot_loss01']]df3[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss02','annual_tot_loss02']]df4[["CNTR_CODE", 'Risk_damage', 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'Risk_damage1','pot_tot_loss10', 'annual_tot_loss10']]df5[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss11','annual_tot_loss11']]df6[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss12','annual_tot_loss12']]df7[["CNTR_CODE", 'Risk_damage', 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'Risk_damage2','pot_tot_loss20', 'annual_tot_loss20']]df8[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss21','annual_tot_loss21']]df9[["CNTR_CODE", 'pot_tot_loss','annual_tot_loss']]=copy_df[["CNTR_CODE", 'pot_tot_loss22','annual_tot_loss22']]new_df=pd.concat([df1, df2,df3,df4,df5,df6,df7,df8,df9]).reset_index() 

Answer 2

首先像这样获取临时数据框df1[["a", "b"]]=df[["a1", "b1"]]df2[["a", "b"]]=df[["a2", "b2"]]这将给出两个数据帧，然后连接两者new_df=pd.concat([df1, df2]).reset_index()