🌐 Mailman 3 December 2004 - Python-list - python.org

Re: built-in 'property'
by Steven Bethard Dec. 31, 2004

Dec. 31, 2004

Stian Søiland wrote: > On 2004-12-28 12:05:20, Bob.Cowdery(a)CGI-Europe.com wrote: > > >>class NOTOK(object): >> >> def __init__(self): >> self.__x = 0 >> self.x = property(self.getx, self.setx, self.delx, "I'm the 'x' >>property.") >> >> def getx(self): return self.__x - 5 >> def setx(self, value): self.__x = value + 10 >> def delx(self): del self.__x I seem to be missing some of the messages on this thread, but while we're talking about properties, it's probably instructive to remind people that the functions passed to the property function are not redefinable in subclasses: py> class D(C): ... def getx(self): ... return 42 ... py> D(5).x 5 py> class C(object): ... def getx(self): ... return 1 ... x = property(getx) ... py> class D(C): ... def getx(self): ... return 42 ... py> C().x 1 py> D().x 1 Note that even though I redefined getx in class D, the 'x' property is still using the function C.getx that was passed into it. For this reason, I usually suggest declaring properties like[1]: py> class E(object): ... def x(): ... def get(self): ... return float(self._x) ... def set(self, x): ... self._x = x**2 ... return dict(fget=get, fset=set) ... x = property(**x()) ... def __init__(self, x): ... self._x = x ... py> e = E(42) py> e.x 42.0 py> e.x = 3 py> e.x 9.0 Note that by using the x = property(**x()) idiom, I don't pollute my class namespace with get/set/del methods that aren't really useful to instances of the class. It also makes it clear to subclasses that if they want different behavior from the x property that they'll need to redefine the entire property, not just a get/set/del method. Steve [1] Thanks to whoever originally suggested this! Sorry, I've forgotten who...

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Securing a future for anonymous functions in Python
by Nick Coghlan Dec. 31, 2004

Dec. 31, 2004

GvR has commented that he want to get rid of the lambda keyword for Python 3.0. Getting rid of lambda seems like a worthy goal, but I'd prefer to see it dropped in favour of a different syntax, rather than completely losing the ability to have anonymous functions. Anyway, I'm looking for feedback on a def-based syntax that came up in a recent c.l.p discussion: http://boredomandlaziness.skystorm.net/2004/12/anonymous-functions-in-pytho… Cheers, Nick. -- Nick Coghlan | ncoghlan(a)email.com | Brisbane, Australia --------------------------------------------------------------- http://boredomandlaziness.skystorm.net

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Re: Pyparsing: Non-greedy matching?
by Paul McGuire Dec. 31, 2004

Dec. 31, 2004

"Peter Fein" <pfein(a)pobox.com> wrote in message news:mailman.8632.1104454752.5135.python-list@python.org... > I'm trying to use pyparsing write a screenscraper. I've got some > arbitrary HTML text I define as opener & closer. In between is the HTML > data I want to extract. However, the data may contain the same > characters as used in the closer (but not the exact same text, > obviously). I'd like to get the *minimal* amount of data between these. > > Here's an example (whitespace may differ): > > from pyparsing import * > > test=r"""<tr class="tableTopSpace"><td></td></tr> > <tr class="tableTitleDark"><td class="tableTitleDark">Job > Information</td></tr><tr><td><table width="100%" border="0" > cellspacing="3"><tr> > <td width="110" valign="top"><div align="right"><strong>Job Title: > </strong></div></td> > <td class="ccDisplayCell">Big Old <B > STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man</td></tr> > <tr> > <td width="110" valign="top"><div align="right"><strong>Employer: > </strong></div></td> > <td width="200" nowrap class="ccDisplayCell"><table><tr><td colspan="2" > valign="top">Global Megacorp</td></tr></table></td><td> > <script> > function escapecomp(){ > } > """ > > data=Combine(OneOrMore(Word(printables)), adjacent=False, > joinString=" ") > > title_open=Literal(r"""<td width="110" valign="top"><div > align="right"><strong>Job Title: </strong></div></td> > <td class="ccDisplayCell">""") > title_open.suppress() > > title_close=Literal(r"""</td>""") > title_close.suppress() > > title=title_open + data + title_close > title2=title_open + (data | title_close) > > >>> title.scanString(test).next() > Traceback (most recent call last): > File "<stdin>", line 1, in ? > StopIteration > > >>> title2.scanString(test).next() > ((['<td width="110" valign="top"><div align="right"><strong>Job Title:\n > </strong></div></td>\n<td class="ccDisplayCell">', 'Big Old <B > STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man</td> </tr> > <tr> <td width="110" valign="top"><div align="right"><strong>Employer: > </strong></div></td> <td width="200" nowrap > class="ccDisplayCell"><table><tr><td colspan="2" valign="top">Global > Megacorp</td></tr></table></td> <td> <script> function escapecomp(){ > }'], {}), 182, 656) > >>> > > I'd expected title to work, but it doesn't match at all. ;( In other > test variants, title2 gives extra stuff at the end though not > necessarily to the end of the string (due to unprintable characters, > perhaps). > > I want a ParseResult more like: > ['<td width="110" valign="top"><div align="right"><strong>Job Title:\n > </strong></div></td>\n<td class="ccDisplayCell">', 'Big Old <B > STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man, '</td>'] > > I sort of understand why title2 works as it does (the OneOrMore just > slurps up everything), but for the life of me I can't figure out how to > fix it. ;) Is there a way of writing something similar to RE's ".*?" ? > > --Pete > > -- > Peter Fein pfein(a)pobox.com 773-575-0694 > > Basically, if you're not a utopianist, you're a schmuck. -J. Feldman Peter - Well you are correct, OneOrMore just keeps on slurping as long as it continues to find matching text. Unlike RE's, it does not look ahead in the RE to treat the next literal as a terminating expression. In the examples that come with pyparsing, there is an HTML extractor (getNTPservers.py) that uses a CharsNotIn("<") expression for the body of an HTML tag. That works for the given case, but wont work for you - the body of your tag also includes other HTML tags, such as <B>, so a CharsNotIn would terminate before the complete body were extracted. Assuming that your <td> tag wont contain any nested <td> tag, you could define your data content as "everything up until I find '</td>'". For this you can use pyparsing's SkipTo element. I think if you define data as: data = SkipTo("</td>") then your code should start working better. There are a couple of other points on your sample code. Note that suppress() is *not* a mutator, but actually a factory method - in expr.suppress(), expr is not modified by suppress, but returns a Suppress object wrapped around an expr. So in place of: title_close=Literal(r"""</td>""") title_close.suppress() you should do title_close=Literal(r"""</td>""").suppress() or title_close=Literal(r"""</td>""") title_close = title_close.suppress() -- Paul

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Re: Securing a future for anonymous functions in Python
by Carl Banks Dec. 31, 2004

Dec. 31, 2004

Nick Coghlan wrote: > GvR has commented that he want to get rid of the lambda keyword for Python 3.0. > Getting rid of lambda seems like a worthy goal, but I'd prefer to see it dropped > in favour of a different syntax, rather than completely losing the ability to > have anonymous functions. I shall either coin or reuse a new term here: "premature optimization of the Python language." (Please note that the word premature is not intended to be an accurate description, but irony by analogy, so spare me any semantic nitpicking.) In much the same way that programmers often spend a lot of time optimizing parts of their program that will yield very minor dividends, while they could have spent that time working on other things that will pay off a lot, many of the wannabe language designers here are spending a lot of time on aspects of the language for which any improvement would only pay small dividends. I think the worry about anonymous functions is one of the most widespread cases of "premature optimization of the Python Language." One could argue about the various benefits of particular choices, maybe even make a convincing case that one is best in accord with the design goals of Python; but in the end, the divends are small compared to improving other aspects of the language. -- CARL BANKS

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RE: Securing a future for anonymous functions in Python
by Batista, Facundo Dec. 31, 2004

Dec. 31, 2004

[Nick Coghlan] #- I just don't understand why people complain so much about #- the restriction to a #- single expression in lambdas, yet there is nary a peep about #- the same #- restriction for generator expressions and list comprehensions. What *I* don't understand (and it could perfectly be plain ignorance, as never studied languages or computer sciences) is why anonymous functions are so important. While I'm one of those who spend 30% of the time writing the function and 70% choosing a name for it, I never really use lambdas (except for minor cases in Tkinter buttons). hoping-to-learn-something-new-in-the-next-mail--ly yours, . Facundo Bitácora De Vuelo: http://www.taniquetil.com.ar/plog PyAr - Python Argentina: http://pyar.decode.com.ar/ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADVERTENCIA. La información contenida en este mensaje y cualquier archivo anexo al mismo, son para uso exclusivo del destinatario y pueden contener información confidencial o propietaria, cuya divulgación es sancionada por la ley. Si Ud. No es uno de los destinatarios consignados o la persona responsable de hacer llegar este mensaje a los destinatarios consignados, no está autorizado a divulgar, copiar, distribuir o retener información (o parte de ella) contenida en este mensaje. Por favor notifíquenos respondiendo al remitente, borre el mensaje original y borre las copias (impresas o grabadas en cualquier medio magnético) que pueda haber realizado del mismo. Todas las opiniones contenidas en este mail son propias del autor del mensaje y no necesariamente coinciden con las de Telefónica Comunicaciones Personales S.A. o alguna empresa asociada. Los mensajes electrónicos pueden ser alterados, motivo por el cual Telefónica Comunicaciones Personales S.A. no aceptará ninguna obligación cualquiera sea el resultante de este mensaje. Muchas Gracias.

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need some help with threading module...
by chahnaz.ourzikene Dec. 31, 2004

Dec. 31, 2004

Hi all, This is the first i post in this newsgroup, i hope my english is not too bad... Let's get straight to the point ! I have a little probleme using threads in my little training example : I wish to create two threads in my application, one thread (the subject) will increment a variable, and another thread (the controller) will print a message saying "i am waiting..." or someting like that, until the counter of the first thread reaches 10 or higher. It will query the first thread object about the value of that counter in a while loop until that counter reaches 10 or higher... Here is the code i wrote (it doesn't work): from threading import * #################################### class Subject(object): def __init__(self) : self.counter = 0 t = Timer(0.00001,self.doIteratingStuff) t.start() def incrementCounter(self,n=1) : self.counter = self.counter + n def doIteratingStuff(self) : for i in range(10) : self.incrementCounter(4) print "the counter is now", self.counter def count(self): return self.counter #################################### class Controller(object): def __init__(self, objectToControl) : self.controlled = objectToControl self.th = Thread(target = self.stopCounting) def start(self): self.th.start() def stopCounting(self): i = 0 #while(1): for i in range(100000) : print "###############################> waiting... ", i i = i + 1 if self.controlled.count() >= 10 : print "it is ten" return #################################### class Application (object) : def __init__(self) : pass def launch(self) : self.sub = Subject() self.control = Controller(self.sub) self.control.start() #################################### a = Application() a.launch() Of course, the indentations are lost since i copied this code from my emacs on linux, and then paste it on my outlook express (i don't have the net on linux :(...). The probleme with the code is that the controler thread never stops !! that's why the while loop is now commented and replaced by a for loop... I wish the problem is clear for all and that somebody can give some help ! Thanks for all and merry x-mas and blablablah. Yacine Chaouche, France.

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getattr() woes
by Thomas Rast Dec. 31, 2004

Dec. 31, 2004

Hello I've found out about a fundamental problem of attribute lookup, the hard way. asyncore.py uses the following code: class dispatcher: # ... def __getattr__(self, attr): return getattr(self.socket, attr) Now suppose that I'm asking for some attribute not provided by dispatcher: The lookup mechanism will apparently try to find it directly and fail, generating an AttributeError; next it will call __getattr__ to find the attribute. So far, no problems. But I used a property much like this: >>> import asyncore >>> class Peer(asyncore.dispatcher): ... def _get_foo(self): ... # caused by a bug, several stack levels deeper ... raise AttributeError('hidden!') ... foo = property(_get_foo) ... and as the error message suggests, the original AttributeError is hidden by the lookup mechanism: >>> Peer().foo Traceback (most recent call last): File "<stdin>", line 1, in ? File "/usr/lib/python2.4/asyncore.py", line 366, in __getattr__ return getattr(self.socket, attr) AttributeError: 'NoneType' object has no attribute 'foo' Is there anything that can be done about this? If there are no better solutions, perhaps the documentation for property() could point out this pitfall? - Thomas -- If you want to reply by mail, substitute my first and last name for 'foo' and 'bar', respectively, and remove '.invalid'.

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Pyparsing: Non-greedy matching?
by Peter Fein Dec. 31, 2004

Dec. 31, 2004

I'm trying to use pyparsing write a screenscraper. I've got some arbitrary HTML text I define as opener & closer. In between is the HTML data I want to extract. However, the data may contain the same characters as used in the closer (but not the exact same text, obviously). I'd like to get the *minimal* amount of data between these. Here's an example (whitespace may differ): from pyparsing import * test=r"""<tr class="tableTopSpace"><td></td></tr> <tr class="tableTitleDark"><td class="tableTitleDark">Job Information</td></tr><tr><td><table width="100%" border="0" cellspacing="3"><tr> <td width="110" valign="top"><div align="right"><strong>Job Title: </strong></div></td> <td class="ccDisplayCell">Big Old <B STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man</td></tr> <tr> <td width="110" valign="top"><div align="right"><strong>Employer: </strong></div></td> <td width="200" nowrap class="ccDisplayCell"><table><tr><td colspan="2" valign="top">Global Megacorp</td></tr></table></td><td> <script> function escapecomp(){ } """ data=Combine(OneOrMore(Word(printables)), adjacent=False, joinString=" ") title_open=Literal(r"""<td width="110" valign="top"><div align="right"><strong>Job Title: </strong></div></td> <td class="ccDisplayCell">""") title_open.suppress() title_close=Literal(r"""</td>""") title_close.suppress() title=title_open + data + title_close title2=title_open + (data | title_close) >>> title.scanString(test).next() Traceback (most recent call last): File "<stdin>", line 1, in ? StopIteration >>> title2.scanString(test).next() ((['<td width="110" valign="top"><div align="right"><strong>Job Title:\n </strong></div></td>\n<td class="ccDisplayCell">', 'Big Old <B STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man</td> </tr> <tr> <td width="110" valign="top"><div align="right"><strong>Employer: </strong></div></td> <td width="200" nowrap class="ccDisplayCell"><table><tr><td colspan="2" valign="top">Global Megacorp</td></tr></table></td> <td> <script> function escapecomp(){ }'], {}), 182, 656) >>> I'd expected title to work, but it doesn't match at all. ;( In other test variants, title2 gives extra stuff at the end though not necessarily to the end of the string (due to unprintable characters, perhaps). I want a ParseResult more like: ['<td width="110" valign="top"><div align="right"><strong>Job Title:\n </strong></div></td>\n<td class="ccDisplayCell">', 'Big Old <B STYLE="background-color:#FFEF95">Head Honcho</B> Boss Man, '</td>'] I sort of understand why title2 works as it does (the OneOrMore just slurps up everything), but for the life of me I can't figure out how to fix it. ;) Is there a way of writing something similar to RE's ".*?" ? --Pete -- Peter Fein pfein(a)pobox.com 773-575-0694 Basically, if you're not a utopianist, you're a schmuck. -J. Feldman

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Re: Other notes
by Mike Meyer Dec. 30, 2004

Dec. 30, 2004

Jp Calderone <exarkun(a)divmod.com> writes: > On Wed, 29 Dec 2004 12:38:02 -0600, Mike Meyer <mwm(a)mired.org> wrote: >>Jp Calderone <exarkun(a)divmod.com> writes: >> > This aside, not even Python 3.0 will be flexible enough to let you define >> > an infix decorator. The language developers are strongly against supporting >> > macros, which is what an infix decorator would amount to. >> >> Could you please explain how allowing new infix operators amount to >> supporting macros? > > You misread - I said "what an infix decorator would amount to". Adding > new infix operators is fine and in no way equivalent to macros. You misread, I said "allowing new infix oerpators amount to supporting macros?" >> > Now, they might be convinced to add a new syntax that makes a function >> > into an infix operator. Perhaps something like this: >> > >> > def &(..)(x, y): >> > return range(x, y + 1) >> >> And while you're at it, explain how this method of defining new infix >> operators differs from using decorators in such a way that it doesn't >> amount to supporting macros. > > Simple. You can't do anything except define a new infix operator with > the hypothetical "def &( <operator> )" syntax. With real macros, you can > define new infix operators, along with any other syntactic construct your > heart desires. You failed to answer the question. We have two proposed methods for adding new infix operators. One uses decorators, one uses a new magic syntax for infix operators. Neither allows you to do anything except declare new decorators. For some reason, you haven't explained yet, you think that using decorators to declare infix operators would amount to macros, yet using a new syntax wouldn't. Both require modifying the grammer of the language accepted by the parser. How is it that one such modification "amounts to macros", whereas the other doesn't? <mike -- Mike Meyer <mwm(a)mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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standard IDE in python 3000 (or beyond)? *semi-newbie*
by mike kreiner Dec. 30, 2004

Dec. 30, 2004

Are there any plans for developing a standard IDE for python that's included with the python installation? I found information about other IDE's elsewhere online, but couldn't even find any mention of this possibility. I'm still relatively new to Python--I switched over from VB--and I found it difficult to learn python without an IDE. Most experienced programmers I know started out using Emacs or another text editor, and are very happy with that; however, I found it difficult to put all the pieces (like GUI, etc.) together myself. i tried many of the free IDEs, but was dissatisfied (VS is tough to beat in my opinion, much better than the average m$ application *plz don't flame*). although it'd be a difficult undertaking, i think an IDE would be a tremendous boost for python in terms of gaining support in education and the business community. has anyone else discussed this? does anyone know the BDFL's stance? thanks. ~mike

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