Pandas adding rows to dataframe

I’m trying to add more rows or records to my data frame, let’s say it looks like this:

ID   age   
44   23
31   25 

and I have a CSV file stored in another data frame without headers

33   55
22   23
29   22

now I want a new data frame that looks like this

ID   age   
44   23
31   25 
33   55
22   23
29   22

I have tried using append and concat but I didn’t get the result that I wanted

Answer

Assuming df1/df2, you can use set_axis to copy the axis of the first DataFrame, then concat:

out = pd.concat([df1, df2.set_axis(df1.columns, axis=1)], ignore_index=True)

output:

   ID  age
0  44   23
1  31   25
2  33   55
3  22   23
4  29   22

NB. ignore_index=True is optional, this is just to avoid having duplicated indices. Without it:

   ID  age
0  44   23
1  31   25
0  33   55
1  22   23
2  29   22