all language changes introduced in each line since the prior edition was publishedand has been polished throughout to update and sharpen its presentation specificallypython coverage here has been updated to include features such as dictionary and set comprehensions that were formerly for onlybut have been back-ported for use in python coverage has been augmented for new yield and raise syntaxthe __pycache__ bytecode model namespace packagespydoc' all-browser modeunicode literal and storage changesand the new windows launcher shipped with assorted new or expanded coverage for jsontimeitpypyos popengeneratorsrecursionweak references__mro____iter__super__slots__metaclassesdescriptorsrandomsphinxand more has been addedalong with general increase in compatibility in both examples and narrative this edition also adds new conclusion as (on python' evolution)two new appendixes (on recent python changes and the new windows launcher)and one new (on benchmarkingan expanded version of the former code timing examplesee appendix for concise summary of python changes between the prior edition and this oneas well as links to their coverage in the book this appendix also summarizes initial differences between and in general that were first addressed in the prior editionthough somesuch as new-style classesspan versions and simply become mandated in (more on what the ' mean in momentper the last bullet in the preceding listthis edition has also experienced some growth because it gives fuller coverage to more advanced language features--which many of us have tried very hard to ignore as optional for the last decadebut which have now grown more common in python code as we'll seethese tools make python more powerfulbut also raise the bar for newcomersand may shift python' scope and definition because you might encounter any of thesethis book covers them head-oninstead of pretending they do not exist despite the updatesthis edition retains most of the structure and content of the prior editionand is still designed to be comprehensive learning resource for both the and python lines while it is primarily focused on users of python and -the latest in the line and the likely last in the line--its historical perspective also makes it relevant to older pythons that still see regular use today though it' impossible to predict the futurethis book stresses fundamentals that have been valid for nearly two decadesand will likely apply to future pythons too as usuali'll be posting python updates that impact this book at the book' website described ahead the "what' newdocuments in python' manuals set can also serve to fill in the gaps as python surely evolves after this book is published preface xxxv