Summary DataFrame all Names years = range (1880 ,2012) frames = [ ] for year in years : frame = pd . r e a d c s v ( ’ / path /yob%d . t x t ’%year , names=[ ’name ’ , ’ sex ’ , ’ b i r t h s ’ ] ) frame [ ’ year ’ ] = year frames . append ( frame ) names = pd . concat ( frames , i g n o r e i n d e x=True ) t o t a l b i r t h s = names . p i v o t t a b l e ( ’ b i r t h s ’ , \ rows=’ year ’ , c o l s=’ sex ’ , aggfunc=sum) t o t a l b i r t h s . p l o t ()