How to merge two dataframe?

Question

DataFrame D1 like:

DataFrame D2 like:

I want to merge them like:

I used pd.concat, get this(This is not what I want):

How can I append C,D..... to every row in a Pandas DataFrame D1.

Answer 1

If you always have only one row in the second dataframe, you can do:

for col in df2:
   df1[col] = np.tile(df2[col].values, len(df1))

Note that tile just repeats the array elements up to a certain length (here len(df1)). This is equivalent to

df2[col].values.tolist() * len(df1)

If you need something more performant and clean, have a look at pandas' merge function.