because of the scopes carved out by the related books just mentionedthis book' scope follows two explicit constraintsit does not cover python language fundamentals it is not intended as language reference the former of these constraints reflects the fact that core language topics are the exclusive domain of learning pythonand encourage you to consult that book before tackling this one if you are completely new to the python languageas its topics are assumed here some language techniques are shown by example in this book tooof courseand the larger examples here illustrate how core concepts come together into realistic programs oopfor exampleis often best sampled in the context of the larger programs we'll write here officiallythoughthis book assumes you already know enough python fundamentals to understand its example code our focus here is mostly on libraries and toolsplease see other resources if the basic code we'll use in that role is unclear the latter of the two constraints listed above reflects what has been common misconception about this book over the years (indeedthis book might have been better titled applying python had we been more clairvoyant in want to make this as clear as canthis is not reference book it is tutorial although you can hunt for some details using the index and table of contentsthis book is not designed for that purpose insteadpython pocket reference provides the sort of quick reference to details that you'll find useful once you start writing nontrivial code on your own there are other reference-focused resources availableincluding other books and python' own reference manuals set herethe goal is gradual tutorial that teaches you how to apply python to common tasks but does not document minute details exhaustively about this fourth edition if this is the first edition of this book you've seenyou're probably less interested in recent changesand you should feel free to skip ahead past this section for readers of prior editionsthoughthis fourth edition of this book has changed in three important waysit' been updated to cover python (onlyit' been slimmed down to sharpen its focus and make room for new topics it' been updated for newly emerged topics and tools in the python world the first of these is probably the most significant--this edition employs the python languageits version of the standard libraryand the common practice of its users to better explain how this and the other two changes take shape in this editionthoughi need to fill in few more details preface xxv