python that offers stunning performance improvements--represent futureif not an outright faction all opinions asidealmost five years after its release has yet to supersede xor even match its user base as one metric is still downloaded more often than for windows at python org todaydespite the fact that this measure would be naturally skewed to new users and the most recent release such statistics are prone to changeof coursebut after five years are indicative of uptake nonetheless the existing software base still trumps ' language extensions for many moreoverbeing last in the line makes sort of de facto standardimmune to the constant pace of change in the line-- positive to those who seek stable baseand negative to those who seek growth and ongoing relevance personallyi think today' python world is large enough to accommodate both and xthey seem to satisfy different goals and appeal to different campsand there is precedence for this in other language families ( and ++for examplehave longstanding coexistencethough they may differ more than python and xmoreoverbecause they are so similarthe skills gained by learning either python line transfer almost entirely to the otherespecially if you're aided by dual-version resources like this book in factas long as you understand how they divergeit' often possible to write code that runs on both at the same timethis split presents substantial dilemma for both programmers and book authorswhich shows no signs of abating while it would be easier for book to pretend that python never existed and cover onlythis would not address the needs of the large python user base that exists today vast amount of existing code was written for python xand it won' be going away anytime soon and while some newcomers to the language can and should focus on python xanyone who must use code written in the past needs to keep one foot in the python world today since it may still be years before many third-party libraries and extensions are ported to python xthis fork might not be entirely temporary coverage for both and to address this dichotomy and to meet the needs of all potential readersthis book has been updated to cover both python and python and should apply to later releases in both the and lines it' intended for programmers using python xprogrammers using python xand programmers stuck somewhere between the two that isyou can use this book to learn either python line although is often emphasized differences and tools are also noted along the way for programmers using older code while the two versions are largely similarthey diverge in some important waysand 'll point these out as they crop up preface xxxvii