The Third Edition’s Python Language Changes

On the language front, the third edition was thoroughly updated to reflect Python 2.5 and all changes to the language since the publication of the second edition in late 2003. (The second edition was based largely on Python 2.2, with some 2.3 features grafted on at the end of the project.) In addition, discussions of anticipated changes in the upcoming Python 3.0 release were incorporated where appropriate. Here are some of the major language topics for which new or expanded coverage was provided (chapter numbers here have been updated to reflect the fourth edition):

 

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  • The new B if A else C conditional expression (Chapter 19)
  • with/as context managers (Chapter 33)
  • try/except/finally unification (Chapter 33)
  • Relative import syntax (Chapter 23)
  • Generator expressions (Chapter 20)
  • New generator function features (Chapter 20)
  • Function decorators (Chapter 31)
  • The set object type (Chapter 5)
  • New built-in functions: sorted, sum, any, all, enumerate (Chapters 13 and 14)
  • The decimal fixed-precision object type (Chapter 5)
  • Files, list comprehensions, and iterators (Chapters 14 and 20)
  • New development tools: Eclipse, distutils, unittest and doctest, IDLE enhancements, Shedskin, and so on (Chapters 2 and 35)

Smaller language changes (for instance, the widespread use of True and False; the new sys.exc_info for fetching exception details; and the demise of string-based exceptions, string methods, and the apply and reduce built-ins) are discussed throughout the book. The third edition also expanded coverage of some of the features that were new in the second edition, including three-limit slices and the arbitrary arguments call syntax that subsumed apply.