Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv14980 Modified Files: pep-0000.txt pep-0308.txt Log Message: Record pronouncement on conditional expressions. Index: pep-0000.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0000.txt,v retrieving revision 1.345 retrieving revision 1.346 diff -u -d -r1.345 -r1.346 --- pep-0000.txt 28 Sep 2005 14:11:28 -0000 1.345 +++ pep-0000.txt 30 Sep 2005 01:51:58 -0000 1.346 @@ -63,6 +63,7 @@ Accepted PEPs (accepted; may not be implemented yet) + SA 308 If-then-else expression GvR, Hettinger SA 328 Imports: Multi-Line and Absolute/Relative Aahz SA 342 Coroutines via Enhanced Generators GvR, Eby SA 343 Anonymous Block Redux and Generator Enhancements GvR @@ -203,7 +204,6 @@ SR 295 Interpretation of multiline string constants Koltsov SR 296 Adding a bytes Object Type Gilbert SR 303 Extend divmod() for Multiple Divisors Bellman - SR 308 If-then-else expression GvR, Hettinger SR 310 Reliable Acquisition/Release Pairs Hudson, Moore SD 312 Simple Implicit Lambda Suzi, Martelli SR 313 Adding Roman Numeral Literals to Python Meyer @@ -353,7 +353,7 @@ SF 305 CSV File API Montanaro, et al I 306 How to Change Python's Grammar Hudson SF 307 Extensions to the pickle protocol GvR, Peters - SR 308 If-then-else expression GvR, Hettinger + SA 308 If-then-else expression GvR, Hettinger SF 309 Partial Function Application Harris S 310 Reliable Acquisition/Release Pairs Hudson, Moore SF 311 Simplified GIL Acquisition for Extensions Hammond Index: pep-0308.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0308.txt,v retrieving revision 1.20 retrieving revision 1.21 diff -u -d -r1.20 -r1.21 --- pep-0308.txt 13 Aug 2003 18:06:34 -0000 1.20 +++ pep-0308.txt 30 Sep 2005 01:51:58 -0000 1.21 @@ -3,14 +3,43 @@ Version: $Revision$ Last-Modified: $Date$ Author: Guido van Rossum, Raymond D. Hettinger -Status: Rejected +Status: Accepted Type: Standards Track Content-Type: text/plain Created: 7-Feb-2003 Post-History: 7-Feb-2003, 11-Feb-2003 +Adding a conditional expression -Introduction + On 9/29/2005, Guido decided to add conditional expressions in the + form of "X if C else Y". [1] + + The motivating use case was the prevalance of error-prone attempts + to achieve the same effect using "and" and "or". [2] + + Previous community efforts to add a conditional expression were + stymied by a lack of consensus on the best syntax. That issue was + resolved by simply deferring to a BDFL best judgment call. + + The decision was validated by reviewing the how the syntax fared when + applied throughout the standard library (this review approximates a + sampling of real-world use cases, across a variety of applications, + written by a number of programmers with diverse backgrounds). [3] + +References + + [1] Pronouncement + http://mail.python.org/pipermail/python-dev/2005-September/056846.html + + [2] Motivating use case: + http://mail.python.org/pipermail/python-dev/2005-September/056546.html + http://mail.python.org/pipermail/python-dev/2005-September/056510.html + + [3] Review in the context of real-world code fragments: + http://mail.python.org/pipermail/python-dev/2005-September/056803.html + + +Introduction to earlier draft of the PEP (kept for historical purposes) Requests for an if-then-else ("ternary") expression keep coming up on comp.lang.python. This PEP contains a concrete proposal of a