Can we insert values of one column from one data frame to another column of another dataframe based on index using python?

Sorry If my English is bad(while trying to explain). I have two different data frames. Say my df1 is,

 a b d 0 1 2 5 1 2 3 9 2 3 4 1 3 1 2 5 4 2 3 9 5 3 4 1 6 1 2 5 7 2 3 9 8 3 4 1 

Second df is,

 xyz 0 23 1 24 2 35 6 17 7 23 8 34 

Now, I only want to replace the values in my df1(column 'a') based on the index of df2.suppose index 0 of df2 has 23 then df1 index 0 has to be changed to 23. I have tried it but I am getting an error. How do I replace the values. My code is below:-

for i in df1.index: for j indf2.index: if i == j: df1.iloc['a'][i] = df2.loc['xyz'][j] print(df1) 

getting a error like

KeyError: 'xyz' During handling of the above exception, another exception occurred: How would I resolve this, Where am I going wrong? 

Output will like this:

 a b d 0 23 2 5 1 24 3 9 2 35 4 1 3 1 2 5 4 2 3 9 5 3 4 1 6 17 2 5 7 23 3 9 8 34 4 1