Two dataframes with different sizes

Question

This is my code for dataframing for both df1 and df2. I'm trying to merge these df1 and df2.

   import pandas as pd
   df1 = pd.read_table("mass2.txt")
   df1.columns =['ID']
   print(df1)
   df2 = pd.read_table("combined.txt",sep=",")
   df2.columns =['Teff','ID']
   print(df2)
   columns_titles = ["ID","Teff"]
   df3=df2.reindex(columns=columns_titles)
   print(df3)
   df4 = df1.merge(df3, on='ID', how='left')
   print(df4)´´´
I need to merge df2 and df1. There are similar IDs in df1 and 
df2 but it's not giving me the respective Teff.
   
I'm getting an output like this:

                     ID Teff
0 J22154748 + 4954052 NaN
1 J22154748 + 4954052 NaN
2 J22152631 + 4958343 NaN
3 J22154748 + 4954052 NaN
4 J22154748 + 4954052 NaN
... ... ...
1122 AP17515104-3446100 NaN
1123 AP17515104-3446100 NaN
1124 J05062845 + 4112062 NaN
1125 J16142485-3141000 NaN
1126 J16142485-3141000 NaN´´´

So, there is nothing in Teff column for similar IDs I have in df1 and df2.

Tron · Answer 1 · 2022-03-09T12:01:59.987

0

You can try using

pd.merge(df1, df2, on=['A'])

If these are two dataframes as df1 and df2

After performing merge it becomes

edited Mar 09 '22 at 12:01

answered Mar 08 '22 at 21:32

Tron

566
6
7

I tried that too. It doesn't give me the second column. – K_ashyap Mar 08 '22 at 21:45
I've edited the answer, you just need to specify the column that you want. – Tron Mar 09 '22 at 02:41
It is still giving me an empty dataframe. Also, I'm reading the input from a text file. – K_ashyap Mar 09 '22 at 09:27
If you can share your code, then I might be able to help more. – Tron Mar 09 '22 at 10:45
I have edited the question – K_ashyap Mar 09 '22 at 11:08
I have edited the answer by changing the dfs, and changed the solution. – Tron Mar 09 '22 at 12:02
I tried this too. It is giving me 284083 rows x 2 columns instead of 1128 rows x 2 columns. If I try df1.merge(df2, on='ID', how='left') the second column is Nan . – K_ashyap Mar 09 '22 at 12:14
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/242789/discussion-between-tron-and-k-ashyap). – Tron Mar 10 '22 at 00:38

Two dataframes with different sizes

1 Answers1