http://stackoverflow.com/questions/15325182/how-to-filter-rows-in-pandas-by-regex
dbstk.loc[dbstk.STKCODE.str.startswith('6'),:]
dbstk.loc[dbstk.STKCODE.str.contains(^[0,3,6]\d{5}$)]
stkdf = stkdf[stkdf['STOCKCODE'].map(lambda x:x[0]=='0' or x[0]=='3' or x[0]=='6')]