Mailman 3 May 2005 - Python-checkins

python/dist/src/Lib/idlelib NEWS.txt, 1.56, 1.57 run.py, 1.31, 1.32
by kbk＠users.sourceforge.net May 5, 2005

May 5, 2005

Update of /cvsroot/python/python/dist/src/Lib/idlelib In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv18826 Modified Files: NEWS.txt run.py Log Message: Use Queue's blocking feature instead of sleeping in the main loop. Patch # 1190163 Michiel de Hoon Index: NEWS.txt =================================================================== RCS file: /cvsroot/python/python/dist/src/Lib/idlelib/NEWS.txt,v retrieving revision 1.56 retrieving revision 1.57 diff -u -d -r1.56 -r1.57 --- NEWS.txt 3 Feb 2005 01:37:13 -0000 1.56 +++ NEWS.txt 5 May 2005 23:29:54 -0000 1.57 @@ -3,6 +3,9 @@ *Release date: XX-XXX-2005* +- run.py: use Queue's blocking feature instead of sleeping in the main + loop. Patch # 1190163 Michiel de Hoon + - Add config-main option to make the 'history' feature non-cyclic. Default remains cyclic. Python Patch 914546 Noam Raphael. Index: run.py =================================================================== RCS file: /cvsroot/python/python/dist/src/Lib/idlelib/run.py,v retrieving revision 1.31 retrieving revision 1.32 diff -u -d -r1.31 -r1.32 --- run.py 21 Dec 2004 22:10:32 -0000 1.31 +++ run.py 5 May 2005 23:29:54 -0000 1.32 @@ -82,9 +82,8 @@ # exiting but got an extra KBI? Try again! continue try: - seq, request = rpc.request_queue.get(0) + seq, request = rpc.request_queue.get(block=True, timeout=0.05) except Queue.Empty: - time.sleep(0.05) continue method, args, kwargs = request ret = method(*args, **kwargs)

1 0

python/nondist/peps pep-0340.txt,1.23,1.24
by gvanrossum＠users.sourceforge.net May 5, 2005

May 5, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv25281 Modified Files: pep-0340.txt Log Message: Mention some rejected ideas (and explain why). Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.23 retrieving revision 1.24 diff -u -d -r1.23 -r1.24 --- pep-0340.txt 4 May 2005 21:00:46 -0000 1.23 +++ pep-0340.txt 5 May 2005 15:39:19 -0000 1.24 @@ -373,12 +373,28 @@ cases work differently; in Python, you cannot save the block for later use, and you cannot test whether there is a block or not. -Alternatives Considered +Alternatives Considered and Rejected - - Many alternatives have been proposed for 'block', including '@' - and no keyword at all. I haven't seen a proposal for another - keyword that I like better than 'block' yet, and not using a - keyword at all makes many folks (including me) uncomfortable. + - Many alternatives have been proposed for 'block'. I haven't + seen a proposal for another keyword that I like better than + 'block' yet. Alas, 'block' is also not a good choice; it is a + rather popular name for variables, arguments and methods. + Perhaps 'with' is the best choice after all? + + - Instead of trying to pick the ideal keyword, the block-statement + could simply have the form: + + EXPR1 as VAR1: + BLOCK1 + + This is at first attractive because, together with a good choice + of function names (like those in the Examples section below) + used in EXPR1, it reads well, and feels like a "user-defined + statement". And yet, it makes me (and many others) + uncomfortable; without a keyword the syntax is very "bland", + difficult to look up in a manual (remember that 'as' is + optional), and it makes the meaning of break and continue in the + block-statement even more confusing. - Phillip Eby has proposed to have the block-statement use an entirely different API than the for-loop, to differentiate @@ -388,6 +404,20 @@ that the block-statement is conceptually a loop -- it supports break and continue, after all. + - This keeps getting proposed: "block VAR1 = EXPR1" instead of + "block EXPR1 as VAR1". That would be very misleading, since + VAR1 does *not* get assigned the value of EXPR1; EXPR1 results + in a generator which is assigned to an internal variable, and + VAR1 is the value returned by successive calls to the __next__() + method of that iterator. + + - Why not change the translation to apply iter(EXPR1)? All the + examples would continue to work. But this makes the + block-statement *more* like a for-loop, while the emphasis ought + to be on the *difference* between the two. Not calling iter() + catches a bunch of misunderstandings, like using a sequence as + EXPR1. + Comparison to Thunks Alternative semantics proposed for the block-statement turn the

1 0

python/nondist/peps pep-0340.txt,1.22,1.23
by gvanrossum＠users.sourceforge.net May 4, 2005

May 4, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv17237 Modified Files: pep-0340.txt Log Message: Fix bug in example 5 found by Reinhold Birkenfeld. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.22 retrieving revision 1.23 diff -u -d -r1.22 -r1.23 --- pep-0340.txt 4 May 2005 01:03:17 -0000 1.22 +++ pep-0340.txt 4 May 2005 21:00:46 -0000 1.23 @@ -568,7 +568,7 @@ Used as follows: - block locking_opening("/etc/passwd", myLock) as f: + block locking_opening(myLock, "/etc/passwd") as f: for line in f: print line.rstrip() @@ -652,9 +652,10 @@ Booth, Fredrik Lundh, Greg Ewing, Holger Krekel, Jason Diamond, Jim Jewett, Josiah Carlson, Ka-Ping Yee, Michael Chermside, Michael Hudson, Neil Schemenauer, Nick Coghlan, Paul Moore, - Phillip Eby, Raymond Hettinger, Samuele Pedroni, Shannon Behrens, - Skip Montanaro, Steven Bethard, Terry Reedy, Tim Delaney, Aahz, - and others. Thanks all for the valuable contributions! + Phillip Eby, Raymond Hettinger, Reinhold Birkenfeld, Samuele + Pedroni, Shannon Behrens, Skip Montanaro, Steven Bethard, Terry + Reedy, Tim Delaney, Aahz, and others. Thanks all for the valuable + contributions! References

1 0

python/dist/src/Lib/test test_class.py, 1.12, 1.13
by mwh＠users.sourceforge.net May 4, 2005

May 4, 2005

Update of /cvsroot/python/python/dist/src/Lib/test In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv2596/Lib/test Modified Files: test_class.py Log Message: Don't use 'is not' to compare strings. (spotted by reading pypy-svn :) Index: test_class.py =================================================================== RCS file: /cvsroot/python/python/dist/src/Lib/test/test_class.py,v retrieving revision 1.12 retrieving revision 1.13 diff -u -d -r1.12 -r1.13 --- test_class.py 19 Jul 2004 16:29:15 -0000 1.12 +++ test_class.py 4 May 2005 11:59:38 -0000 1.13 @@ -353,7 +353,7 @@ try: A().a # Raised AttributeError: A instance has no attribute 'a' except AttributeError, x: - if str(x) is not "booh": + if str(x) != "booh": print "attribute error for A().a got masked:", str(x) class E:

1 0

python/nondist/peps pep-0340.txt,1.21,1.22
by gvanrossum＠users.sourceforge.net May 4, 2005

May 4, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv15670 Modified Files: pep-0340.txt Log Message: Clarify that there are some separable items. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.21 retrieving revision 1.22 diff -u -d -r1.21 -r1.22 --- pep-0340.txt 3 May 2005 23:51:54 -0000 1.21 +++ pep-0340.txt 4 May 2005 01:03:17 -0000 1.22 @@ -22,6 +22,21 @@ (Reliable Acquisition/Release Pairs), and PEP 325 (Resource-Release Support for Generators). + I should clarify that there are a few separable proposals in this + PEP. + + - Using "continue EXPR" which calls its.__next__(EXPR) which + becomes the return value of a yield-expression is entirely + orthogonal with the rest of the PEP. + + - Similarly, using a generator to "drive" a block statement is + also separable; with just the definition of the block statement + from the PEP you could implement all the examples using a class + (similar to example 6, which is easily turned into a template). + + But the key idea is using a generator to drive a block statement; + the rest is elaboration. + Motivation and Summary (Thanks to Shane Hathaway -- Hi Shane!)

1 0

python/nondist/peps pep-0340.txt,1.20,1.21
by gvanrossum＠users.sourceforge.net May 3, 2005

May 3, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv31381 Modified Files: pep-0340.txt Log Message: Fix a remnant of the old proposal found by Tim Delaney. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.20 retrieving revision 1.21 diff -u -d -r1.20 -r1.21 --- pep-0340.txt 3 May 2005 22:23:32 -0000 1.20 +++ pep-0340.txt 3 May 2005 23:51:54 -0000 1.21 @@ -327,14 +327,14 @@ body. When __next__() is called with an argument that is not None, the - yield-expression that it resumes will return the value attribute - of the argument. If it resumes a yield-statement, the value is - ignored (this is similar to ignoring the value returned by a - function call). When the *initial* call to __next__() receives an - argument that is not None, TypeError is raised; this is likely - caused by some logic error. When __next__() is called without an - argument or with None as argument, and a yield-expression is - resumed, the yield-expression returns None. + yield-expression that it resumes will return the argument. If it + resumes a yield-statement, the value is ignored (this is similar + to ignoring the value returned by a function call). When the + *initial* call to __next__() receives an argument that is not + None, TypeError is raised; this is likely caused by some logic + error. When __next__() is called without an argument or with None + as argument, and a yield-expression is resumed, the + yield-expression returns None. When a generator that has not yet terminated is garbage-collected (either through reference counting or by the cyclical garbage

1 0

python/nondist/peps pep-0340.txt,1.19,1.20
by gvanrossum＠users.sourceforge.net May 3, 2005

May 3, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv8496 Modified Files: pep-0340.txt Log Message: Some clarifications after Raymond's email. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.19 retrieving revision 1.20 diff -u -d -r1.19 -r1.20 --- pep-0340.txt 3 May 2005 18:31:34 -0000 1.19 +++ pep-0340.txt 3 May 2005 22:23:32 -0000 1.20 @@ -122,7 +122,7 @@ will be translated as follows: itr = iter(EXPR1) - arg = None + arg = None # Set by "continue EXPR2", see below brk = False while True: try: @@ -496,7 +496,7 @@ block locking(myLock): # Code here executes with myLock held. The lock is # guaranteed to be released when the block is left (even - # if by an uncaught exception). + # if via return or by an uncaught exception). 2. A template for opening a file that ensures the file is closed when the block is left: @@ -557,6 +557,11 @@ for line in f: print line.rstrip() + (If this example confuses you, consider that it is equivalent + to using a for-loop with a yield in its body in a regular + generator which is invoking another iterator or generator + recursively; see for example the source code for os.walk().) + 6. It is possible to write a regular iterator with the semantics of example 1: @@ -581,6 +586,10 @@ self.lock.release() raise type, value, traceback + (This example is easily modified to implement the other + examples; it shows how much simpler generators are for the same + purpose.) + 7. Redirect stdout temporarily: def redirecting_stdout(new_stdout): @@ -597,6 +606,30 @@ block redirecting_stdout(f): print "Hello world" + 8. A variant on opening() that also returns an error condition: + + def opening_w_error(filename, mode="r"): + try: + f = open(filename, mode) + except IOError, err: + yield None, err + else: + try: + yield f, None + finally: + f.close() + + Used as follows: + + block opening_w_error("/etc/passwd", "a") as f, err: + if err: + print "IOError:", err + else: + f.write("guido::0:0::/:/bin/sh\n") + + 9. More examples are needed: showing "continue EXPR", and the use + of continue, break and return in a block-statement. + Acknowledgements In no useful order: Alex Martelli, Barry Warsaw, Bob Ippolito,

1 0

python/nondist/peps pep-0340.txt,1.18,1.19
by gvanrossum＠users.sourceforge.net May 3, 2005

May 3, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv13580 Modified Files: pep-0340.txt Log Message: Clarify that the block-statement is a loop to the parser, and don't use literally translated Dutch. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.18 retrieving revision 1.19 diff -u -d -r1.18 -r1.19 --- pep-0340.txt 3 May 2005 17:21:13 -0000 1.18 +++ pep-0340.txt 3 May 2005 18:31:34 -0000 1.19 @@ -185,9 +185,11 @@ Note that the 'as' keyword is not contentious (it will finally be elevated to proper keyword status). - Note that it is left in the middle whether a block-statement - represents a loop or not; this is up to the iterator, but in the - most common case BLOCK1 is executed exactly once. + Note that it is up to the iterator to decide whether a + block-statement represents a loop with multiple iterations; in the + most common use case BLOCK1 is executed exactly once. To the + parser, however, it is always a loop; break and continue return + transfer to the block's iterator (see below for details). The translation is subtly different from the translation of a for-loop: iter() is not called, so EXPR1 should already be an

1 0

python/nondist/peps pep-0340.txt,1.17,1.18
by gvanrossum＠users.sourceforge.net May 3, 2005

May 3, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv29297 Modified Files: pep-0340.txt Log Message: saving_stdout -> redirecting_stdout (Phillip Eby). Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.17 retrieving revision 1.18 diff -u -d -r1.17 -r1.18 --- pep-0340.txt 3 May 2005 16:57:17 -0000 1.17 +++ pep-0340.txt 3 May 2005 17:21:13 -0000 1.18 @@ -581,7 +581,7 @@ 7. Redirect stdout temporarily: - def saving_stdout(new_stdout): + def redirecting_stdout(new_stdout): save_stdout = sys.stdout try: sys.stdout = new_stdout @@ -592,7 +592,7 @@ Used as follows: block opening(filename, "w") as f: - block saving_stdout(f): + block redirecting_stdout(f): print "Hello world" Acknowledgements

1 0

python/nondist/peps pep-0340.txt,1.16,1.17
by gvanrossum＠users.sourceforge.net May 3, 2005

May 3, 2005

Update of /cvsroot/python/python/nondist/peps In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv24156 Modified Files: pep-0340.txt Log Message: Add another example (saving sys.stout). Eradicate tabs. Index: pep-0340.txt =================================================================== RCS file: /cvsroot/python/python/nondist/peps/pep-0340.txt,v retrieving revision 1.16 retrieving revision 1.17 diff -u -d -r1.16 -r1.17 --- pep-0340.txt 3 May 2005 16:32:24 -0000 1.16 +++ pep-0340.txt 3 May 2005 16:57:17 -0000 1.17 @@ -558,26 +558,42 @@ 6. It is possible to write a regular iterator with the semantics of example 1: - class locking: - def __init__(self, lock): - self.lock = lock - self.state = 0 - def __next__(self, arg=None): - # ignores arg - if self.state: - assert self.state == 1 - self.lock.release() - self.state += 1 - raise StopIteration - else: - self.lock.acquire() - self.state += 1 - return None - def __exit__(self, type, value=None, traceback=None): - assert self.state in (0, 1, 2) - if self.state == 1: - self.lock.release() - raise type, value, traceback + class locking: + def __init__(self, lock): + self.lock = lock + self.state = 0 + def __next__(self, arg=None): + # ignores arg + if self.state: + assert self.state == 1 + self.lock.release() + self.state += 1 + raise StopIteration + else: + self.lock.acquire() + self.state += 1 + return None + def __exit__(self, type, value=None, traceback=None): + assert self.state in (0, 1, 2) + if self.state == 1: + self.lock.release() + raise type, value, traceback + + 7. Redirect stdout temporarily: + + def saving_stdout(new_stdout): + save_stdout = sys.stdout + try: + sys.stdout = new_stdout + yield + finally: + sys.stdout = save_stdout + + Used as follows: + + block opening(filename, "w") as f: + block saving_stdout(f): + print "Hello world" Acknowledgements

1 0