Mailman 3 October 2001 - Python-Dev

conditional expressions?
by Skip Montanaro Oct. 17, 2001

Oct. 17, 2001

Is the thread in c.l.py on conditional expressions leading in the direction of actually getting added to the language, or wer Tim's experiments done just to show it's possible? Skip

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Conditional expressions and sequences
by Paul F. Dubois Oct. 16, 2001

Oct. 16, 2001

One of the most cherished of Numpy operations is: x = where (condition, t, f) which creates an array x, shaped like condition. Each element of this result is set to the corresponding element of t or f depending on whether the corresponding element of condition is true or false. Either or both of t and f can be a scalar but otherwise must be the same shape as condition. The reason this is cherished is, of course, that it avoids a scalar loop with an if-test in it. Scalar loops make Nummies cringe. Now in your new syntax this is essentially x = if condition then t else f Therefore it would be cool if the implementation was x=condition.__where__(t,f). This slot could be overwritten by classes like Numeric's array. If condition was a list this might be useful too. Never mind how I spelled __where__, please. The naming would require thought. Ducking-down-behind-the-barricade-'ly yours, Paul P.S. I once learned a language where you could say x = y if c and it was yummy.

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What happened to Guido's plans for (S1; S2; ...; Sn; E) ?
by Hamish Lawson Oct. 16, 2001

Oct. 16, 2001

The current discussion on conditional expressions has at times touched on the ever-recurring issue of assignment in expressions. It reminded me that a proposal by Kevin Digweed back in early 1999 had actually managed to obtain Guido's approval as a reasonably Pythonic approach to allowing assignment in expressions, and the proposal seemed intended to make its eventual way into Python. Is this still the case? Kevin's original proposal: | What about allowing an optional "assignment only" suite | between "while" and the test condition. This suite will be executed | before testing the condition each time | <http://groups.google.com/groups?hl=en&selm=78naok%242ed%241%40nnrp1.dejanew…> Guido then expanded on the proposal and seemed to give it his approval: | Why stop there? It could easily be any number of "small" statements | separated by semicolons with the restriction that the final one must | be an expression and that the ones before it must not be flow-control | statements (return, raise, continue, break). Other useful statements | to allow are print (for debugging) and assert, and for all I care | import, del, pass, and exec. | | Note that I like this for 2.0, not so much for for 1.6 (if only | because I don't want 1.6 to make existing books obsolete). | <http://groups.google.com/groups?hl=en&selm=199902021501.KAA07333%40eric.cnr…> Guido also clarified its intended syntax and semantics: | In my interpretation, the expression (S1; S2; ...; Sn; E) yields the | value of expression E -- S1-Sn are only there for their side effects. | <http://groups.google.com/groups?hl=en&selm=199902031343.IAA09480%40eric.cnr…> Hamish Lawson ____________________________________________________________ Do You Yahoo!? Get your free @yahoo.co.uk address at http://mail.yahoo.co.uk or your free @yahoo.ie address at http://mail.yahoo.ie

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New socketmodule.c warnings
by Skip Montanaro Oct. 15, 2001

Oct. 15, 2001

Just came across these new warnings (gcc 2.96, Linux Mandrake): .../Modules/socketmodule.c:1625: warning: initialization from incompatible pointer type .../Modules/socketmodule.c:1629: warning: initialization from incompatible pointer type .../Modules/socketmodule.c:1636: warning: initialization from incompatible pointer type .../Modules/socketmodule.c:1639: warning: initialization from incompatible pointer type .../Modules/socketmodule.c:1642: warning: initialization from incompatible pointer type .../Modules/socketmodule.c:1645: warning: initialization from incompatible pointer type I see a lot of interface changes in socketmodule between 1.175 and 1.176. Is this a spurious error or something significant? Skip

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Problem with Py_NewInterpreter
by Skip Montanaro Oct. 15, 2001

Oct. 15, 2001

Don't know why it got posted where it did (in the mysql-python forum on SF), but some guy posted a question/problem about executing Py_NewInterpreter twice. I have no experience with this sort of stuff, so I figured I'd forward it along to the people with the smarts in this area: http://sourceforge.net/forum/message.php?msg_id=249171 (Need I say, "don't respond to me"? ;-) Skip

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Where is PyMarshal_ReadShortFromFile() ?
by James C. Ahlstrom Oct. 15, 2001

Oct. 15, 2001

I am looking at Python 2.2a3. In Include/, marshal.h declares both PyMarshal_ReadLongFromFile() and PyMarshal_ReadShortFromFile(), but the second seems to be missing from marshal.c. Or is it somewhere else? Here is the code; put in marshal.c just before ReadLongFromFile at line 638: int PyMarshal_ReadShortFromFile(FILE *fp) { RFILE rf; rf.fp = fp; return r_short(&rf); } Jim Ahlstrom

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Will Ware alive? (was Re: where lives uthread (microthreads) now ??)
by aahz＠panix.com Oct. 15, 2001

Oct. 15, 2001

[x-posted to c.l.py and python-dev] In article <3b091a1c.0110080739.23205b07(a)posting.google.com>, cmkl <cmkleffner(a)gmx.de> wrote: > >I wanted to test a samle code with microthreads needed. >The download area: http://world.std.com/~wware/uthread.html >is not available however. > >Is there a mirror to get this code somewhere? Has anybody heard from Will Ware since 9/12? E-mail to him doesn't bounce, but I haven't received any reply. -- --- Aahz <*> (Copyright 2001 by aahz(a)pobox.com) Hugs and backrubs -- I break Rule 6 http://www.rahul.net/aahz/ Androgynous poly kinky vanilla queer het Pythonista We must not let the evil of a few trample the freedoms of the many. -- --- Aahz <*> (Copyright 2001 by aahz(a)pobox.com) Hugs and backrubs -- I break Rule 6 http://www.rahul.net/aahz/ Androgynous poly kinky vanilla queer het Pythonista We must not let the evil of a few trample the freedoms of the many.

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conditional expressions (RE: Loop-and-a-half (Re: Curious assignment behaviour))
by Tim Peters Oct. 14, 2001

Oct. 14, 2001

[Tim] > If people sign off on taking "then" as a new keyword, I think > the chances are good that we could get > > x = if e1 then e2 else e3 > > into 2.2b1. That's the only obvious spelling, hence the only > truly Pythonic way to spell it. Other languages spelling it that > way range from Algol-60 (Guido's first intense language affair) to > Haskell. [Paul Rubin, among others of similar mind] > This sounds fine to me. Alas, it didn't to Python's parser -- one-token lookahead isn't enough to distinguish if 1: from if 1 then 2 else 3 let alone if a + b / c: from if a + b / c then 2 else 3 etc. and Python won't grow anything a simple parser can't sort out. Everything's cool if parens are required around a conditional expression, though, in which case: x = if e1 then e2 else e3 + 1 # SyntaxError x = (if e1 then e2 else e3) + 1 # cool x = (if e1 then e2 else e3 + 1) # cool x = if e1 then e2 else e3 # SyntaxError x = (if e1 then e2 else e3) # cool x = if if e1 then e2 else e3 then e4 else e5 # SyntaxError x = (if (if e1 then e2 else e3) then e4 else e5) # cool Seems a mixed bag, but I'm more interested in readability and the functionality than in minimizing keystrokes; requiring parens doesn't hurt the goals I care about. implemented-but-not-checked-in-ly y'rs - tim

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[development doc updates]
by Fred L. Drake Oct. 14, 2001

Oct. 14, 2001

The development version of the documentation has been updated: http://python.sourceforge.net/devel-docs/ Added documentation for the PyMarshal_*() functions in the Python/C API.

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UM SITE DE PROTESTO
by Keila - Curitiba - Pr Oct. 14, 2001

Oct. 14, 2001

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