out[ ]aapl jnj spx nan xom in [ ]vwap dropna(out[ ]aapl jnj xom since spx wasn' found in volumeyou can choose to explicitly discard that at any point should you wish to align by handyou can use dataframe' align methodwhich returns tuple of reindexed versions of the two objectsin [ ]prices align(volumejoin='inner'out[ ]aapl jnj xom aapl jnj xom another indispensable feature is constructing dataframe from collection of potentially differently indexed seriesin [ ] series(range( )index=[' '' '' ']in [ ] series(range( )index=[' '' '' '' ']in [ ] series(range( )index=[' '' '' ']in [ ]dataframe({'one' 'two' 'three' }out[ ]one three two nan nan nan nan nan nan nan nan as you have seen earlieryou can of course specify explicitly the index of the resultdiscarding the rest of the datain [ ]dataframe({'one' 'two' 'three' }index=list('face')out[ ]one three two nan nan nan nan nan data munging topics www it-ebooks info