如何将两个不同的数据框 df1 df2 与特定列（列 w）进行比较，并从 df2 更新 df1 中匹配的行列 AD

Question

df1
A   B    C  D  E  F  
1   xyz  y  z  0  1
1   xab  z  z  0  1
2   xyz  x  p  1  1
3   xmn  m  q  2  1
3   xyx  n  r  3  1

df2
A   B    C  D  E  F  
1   xyz  x  z  4  1
1   xab  y  q  3  2
2   xyz  z  p  8  3
3   xmn  q  m  1  4
3   xyx  r  r  32  5

expected Output DF1

df1
A   B    C  D  E  F  
1   xyz  y  z  4  1
1   xab  z  z  4  1
2   xyz  x  p  8  1
3   xmn  m  q  3  1
3   xyx  n  r  32  1

i have tried df1.combine_first(df2) not working as expected

Answer 1

Looking at your output I assume that you want to merge the datasets. . . ?

import pandas as pd

d = {'A': [1, 1, 2, 3, 3], 
     'B': ['xyz', 'xab', 'xyz', 'xmn', 'xyx'],
     'C': ['y', 'z', 'x', 'm', 'n'],
     'D': ['z', 'z', 'p', 'q', 'r'],
     'E': [0, 0, 1, 2, 3],
     'F': [1, 1, 1, 1, 1]}
df1 = pd.DataFrame(data=d)
d = {'A': [1, 1, 2, 3, 3], 
     'B': ['xyz', 'xab', 'xyz', 'xmn', 'xyx'],
     'C': ['x', 'y', 'z', 'q', 'r'],
     'D': ['z', 'q', 'p', 'm', 'r'],
     'E': [4, 3, 8, 1, 32],
     'F': [1, 2, 3, 4, 5]}
df2 = pd.DataFrame(data=d)

df1 = df1.merge(df2[['D', 'E']], how='inner', on='D')
df1['E'] = df1['E_y']
del df1['E_x'], df1['E_y']

Output

Out[41]: 
   A    B  C  D  F   E
0  1  xyz  y  z  1   4
1  1  xab  z  z  1   4
2  2  xyz  x  p  1   8
3  3  xmn  m  q  1   3
4  3  xyx  n  r  1  32