used to combine together many dataframe objects having the same or similar indexes but non-overlapping columns in the prior examplewe could have writtenin [ ]left join(right how='outer'out[ ]ohio nevada missouri alabama nan nan nan nan nan nan in part for legacy reasons (much earlier versions of pandas)dataframe' join method performs left join on the join keys it also supports joining the index of the passed dataframe on one of the columns of the calling dataframein [ ]left join(right on='key'out[ ]key value group_val nan lastlyfor simple index-on-index mergesyou can pass list of dataframes to join as an alternative to using the more general concat function described belowin [ ]another dataframe([[ ][ ][ ][ ]]index=[' '' '' '' ']columns=['new york''oregon']in [ ]left join([right another]out[ ]ohio nevada missouri alabama new york nan nan oregon in [ ]left join([right another]how='outer'out[ ]ohio nevada missouri alabama new york oregon nan nan nan nan nan nan nan nan nan nan nan nan nan nan data wranglingcleantransformmergereshape www it-ebooks info