Answers for "pandas concat arbirary number of dataframes"

join on column pandas

# df1 as main df and use the feild from df2 and map it into df1

df1.merge(df2,on='columnName',how='left')

how to append a dataframe to another dataframe in pandas

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