pandas row concatenation code example
Example 1: merge dataframe pandas
>>> df1.merge(df2, left_on='lkey', right_on='rkey')
lkey value_x rkey value_y
0 foo 1 foo 5
1 foo 1 foo 8
2 foo 5 foo 5
3 foo 5 foo 8
4 bar 2 bar 6
5 baz 3 baz 7
Example 2: pandas concat and reset index
train_df = pd.concat(train_class_df_list, ignore_index=True)