I have sample dataframe like this
df1=
A B C
a 1 2
b 3 4
b 5 6
c 7 8
d 9 10
I would like to replace a part of this dataframe (col A=a and b) with this dataframe
df2=
A B C
b 9 10
b 11 12
c 13 14
I would like to get result below
df3=
A B C
a 1 2
b 9 10
b 11 12
c 13 14
d 9 10
I tried
df1[df1.A.isin("bc")]...
But I couldnt figure out how to replace. someone tell how to replace dataframe.
As I explained try update.
import pandas as pd
df1 = pd.DataFrame({"A":['a','b','b','c'], "B":[1,2,4,6], "C":[3,2,1,0]})
df2 = pd.DataFrame({"A":['b','b','c'], "B":[100,400,300], "C":[39,29,100]}).set_index(df1.loc[df1.A.isin(df2.A),:].index)
df1.update(df2)
Out[75]:
A B C
0 a 1.0 3.0
1 b 100.0 39.0
2 b 400.0 29.0
3 c 300.0 100.0
You need combine_first or update by column A, but because duplicates need cumcount:
df1['g'] = df1.groupby('A').cumcount()
df2['g'] = df2.groupby('A').cumcount()
df1 = df1.set_index(['A','g'])
df2 = df2.set_index(['A','g'])
df3 = df2.combine_first(df1).reset_index(level=1, drop=True).astype(int).reset_index()
print (df3)
A B C
0 a 1 2
1 b 9 10
2 b 11 12
3 c 13 14
4 d 9 10
Another solution:
df1['g'] = df1.groupby('A').cumcount()
df2['g'] = df2.groupby('A').cumcount()
df1 = df1.set_index(['A','g'])
df2 = df2.set_index(['A','g'])
df1.update(df2)
df1 = df1.reset_index(level=1, drop=True).astype(int).reset_index()
print (df1)
A B C
0 a 1 2
1 b 9 10
2 b 11 12
3 c 13 14
4 d 9 10
If duplicatesof column A in df1 are same in df2 and have same length:
df2.index = df1.index[df1.A.isin(df2.A)]
df3 = df2.combine_first(df1)
print (df3)
A B C
0 a 1.0 2.0
1 b 9.0 10.0
2 b 11.0 12.0
3 c 13.0 14.0
4 d 9.0 10.0
you could solve your problem with the following:
import pandas as pd
df1 = pd.DataFrame({'A':['a','b','b','c','d'],'B':[1,3,5,7,9],'C':[2,4,6,8,10]})
df2 = pd.DataFrame({'A':['b','b','c'],'B':[9,11,13],'C':[10,12,14]}).set_index(df1.loc[df1.A.isin(df2.A),:].index)
df1.loc[df1.A.isin(df2.A), ['B', 'C']] = df2[['B', 'C']]
Out[108]:
A B C
0 a 1 2
1 b 9 10
2 b 11 12
3 c 13 14
4 d 9 10
assignorupdate