Add a column in a dataframe from another dataframe - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/forum-7.html) +--- Forum: General Coding Help (https://python-forum.io/forum-8.html) +--- Thread: Add a column in a dataframe from another dataframe (/thread-21606.html) |
Add a column in a dataframe from another dataframe - Bilsix - Oct-07-2019 Hi there, I'm a newbie in Python and I need your help. I tried to search my answer in the forum but I think I don't have the good keywords... It's a shame because the issue seems to be simple (but I'm even not sure of this !). Here's the problem : I work with 2 dataframes df1 and df2. df1 has n rows and 3 columns (A has only "NaN") : ColA |ColB| ColC _____________________________ NaN | B4 | C1 NaN | B4 | C2 NaN | B1 | C3 ...... | .... | .... NaN | B39 | C(n-1) NaN | B74 | Cn df2 has n rows and 2 columns (A and B) : ColA|ColB ____________________ A1 | B1 A2 | B2 A3 | B3 .... | .... A(n-1) | B(n-1) An | Bn The goal here is to fill the A column from df1 thanks to df2 and to get a dataframe like this : df1 wanted : ColA|ColB| ColC _____________________________ A4 | B4 | C1 A4 | B4 | C2 A1 | B1 | C3 .... | .... | .... A74 | B74 | Cn I tried a lot of things (double for loops, pandas methods, etc.) but nothing worked. I think I don't have enough experience. Someone can direct me towards the good way to solve the issue ? Thanks ! Bilsix. RE: Add a column in a dataframe from another dataframe - stullis - Oct-07-2019 Hiya, Bilsix! You want to join two tables together. Use the DataFrame.join() method to join them together. This method will create a new DataFrame so be sure to store it. RE: Add a column in a dataframe from another dataframe - Bilsix - Oct-08-2019 Hi stullis, This method does exactly what I want ! Thanks a lot ! I solved my issue temporarely with a double for loop, but I'll use the "join" method, which is much more clear. |