Here is time parsing csv with regexCSV and standard CSV: time ruby regexCSV.rb 26908 real 0m10.072s user 0m9.414s sys 0m0.660s [root@taamportable GMS]# time ruby standardCSV.rb 26907 real 1m48.296s user 1m36.853s sys 0m11.188s Significantly higher than python csv (which is written in c) [root@taamportable GMS]# time python x.py 26907 real 0m0.311s user 0m0.302s sys 0m0.009s