Pandas combine two dataframes to update values of a particular column in 1st dataframe

Question

I have two dataframes:


df1 :
    A     B     C
0   a0    b0    c0
1   a1    b1    c1
2   a2    b2    c2
3   a3    b3    c3
4   a4    b4    c4

df2 :
    A     B     C
0   a0    b0    c11
1   a1    b1    c5
2   a70   b2    c20
3   a3    b9    c9

In df1, for every row, whenever Column A and Column B values are equal to values in df2, column C should be updated with value from df2.

Output:
    A     B     C
0   a0    b0    c11
1   a1    b1    c5
2   a2    b2    c2
3   a3    b3    c3
4   a4    b4    c4

I tried the following, but it did not work.

df1.set_index(['A', 'B'])
df2.set_index(['A', 'B'])
df1.update(df2)
df1.reset_index()
df2.reset_index()

Your solution is right. You need to assign to df1 and df2, when setting the index. From your code above, it seems that you did not. I will delete my answer, because it is not needed. You got the solution right. — sammywemmy
– sammywemmy, Commented Dec 5, 2020 at 21:44

ombk · Accepted Answer · 2020-12-05 17:55:49Z

1

df1["C"][:4] = np.where((df1["A"][:4]==df2["A"])&(df1["B"][:4]==df2["B"]),df2["C"],df1["C"][:4])


    A   B   C
0   a0  b0  c11
1   a1  b1  c5
2   a2  b2  c2
3   a3  b3  c3
4   a4  b4  c4

answered Dec 5, 2020 at 17:55

ombk

2,1091 gold badge6 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Donald Duck is with Ukraine Over a year ago

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value.

ombk Over a year ago

@DonaldDuck once the OP answers i will be more than happy to explain everything

Collectives™ on Stack Overflow

Pandas combine two dataframes to update values of a particular column in 1st dataframe

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related