Replace rows in a Pandas df with rows from another df

Question

I have 2 Pandas dfs, A and B. Both have 10 columns and the index 'ID'. Where the IDs of A and B match, I want to replace the rows of B with the rows of A. I have tried to use pd.update, but no success yet. Any help appreciated.

Answer 1

below code should do the trick

s1 = pd.Series([5, 1, 'a'])
s2 = pd.Series([6, 2, 'b'])
s3 = pd.Series([7, 3, 'd'])
s4 = pd.Series([8, 4, 'e'])
s5 = pd.Series([9, 5, 'f'])



df1 = pd.DataFrame([list(s1), list(s2),list(s3),list(s4),list(s5)],  columns =  ["A", "B", "C"])

s1 = pd.Series([5, 6, 'p'])
s2 = pd.Series([6, 7, 'q'])
s3 = pd.Series([7, 8, 'r'])
s4 = pd.Series([8, 9, 's'])
s5 = pd.Series([9, 10, 't'])

df2 = pd.DataFrame([list(s1), list(s2),list(s3),list(s4),list(s5)],  columns =  ["A", "B", "C"])

df1.loc[df1.A.isin(df2.A), ['B', 'C']] = df2[['B', 'C']]
print df1

output

   A   B  C
0  5   6  p
1  6   7  q
2  7   8  r
3  8   9  s
4  9  10  t

Edit from comments:

To replace the whole row instead of only some columns:

cols = list(df1.columns) 
df1.loc[df1.A.isin(df2.A), cols] = df2[cols]