join data by stackung data panda code example

Example 1: pd merge on multiple columns

new_df = pd.merge(A_df, B_df,  how='left', left_on=['A_c1','c2'], right_on = ['B_c1','c2'])

Example 2: how to append a dataframe to another dataframe in pandas

# all_res is list of DataFrames : [ dataframe, dataframe, ... ]
df_res = pd.concat(all_res)