The append method does not change either of the original DataFrames. Instead, it returns a new DataFrame by appending the original two. Appending a DataFrame to another one is quite simple: In [9]: df1.append(df2) Out[9]: A B C 0 a1 b1 NaN 1 a2 b2 NaN 0 NaN b1 c1 Create empty Dataframe, append rows. Pandas version used: 1.0.3. There are many ways to build and initialize a pandas DataFrame. Here are some of the most common ones: All examples can be found on this notebook. Create from lists.