Mailman 3 May 2007 - Python-ideas

Re: [Python-ideas] Positional only arguments
by George Sakkis May 18, 2007

May 18, 2007

On 5/16/07, Benji York <benji(a)zope.com> wrote: > Guido van Rossum wrote: > > Personally, when I really wanted this, I've given the arguments names > > like __foo. > > That could be enshrined as the syntax, much like "private" attributes. What's the future of "private" attributes in Py3K ? I remember Raymond Hettinger bringing up a challenge on c.l.py about a decorator that could replace the double underscore mangling and Michele Simionato caming up with a bytecode hack that showed it is possible. If they're staying though, +epsilon for blessing __args as positional-only (for some positive epsilon ;-)). George -- "If I have been able to see further, it was only because I stood on the shoulders of million monkeys."

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dot bend spoon
by Aaron Brady May 16, 2007

May 16, 2007

Is the going semantic to carry a relation: spoon.bend() or johnson.bend( spoon ) ? How to phrase this. How do -you- do it? Weird. Because spoon.bend() is a misnomer; construed to mean spoon.getsbent(). More in the predicate vs. controller category. Haven't got model-view-controller yet but I know the term.

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Re: [Python-ideas] parameter omit
by Ron Adam May 15, 2007

May 15, 2007

Aaron Brady wrote: >> -----Original Message----- >> From: Aaron Brady [mailto:castironpi@comcast.net] >> Sent: Sunday, May 13, 2007 9:28 PM >> >>> -----Original Message----- >>> From: python-ideas-bounces(a)python.org [mailto:python-ideas- >>> bounces(a)python.org] On Behalf Of Aaron Brady >>> >>> class GuardDefault: >>> Val= object() >>> def __call__( self, *args, **kwargs ): >>> args=list(args) >>> for i,j in enumerate( args ): >>> if j is GuardDefault.Val: >>> offset= >>> self.callable.func_code.co_argcount-\ >>> len(self.callable.func_defaults) >>> args[i]= >>> self.callable.func_defaults[i-offset] >>> return self.callable( *args,**kwargs ) >>> def __init__( self,callable ): >>> self.callable= callable >> Do you have any interest in pursuing this? > > Actually not too bad for functools. Does this take a proposal? -I- am > God-awful at lengthy technical writing. I suggest you post it on the python-list firsts and see what others think. They may offer alternative ways of doing it that will make it better based on how they will used it. Cheers, Ron

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Re: [Python-ideas] parameter omit
by Aaron Brady May 14, 2007

May 14, 2007

> -----Original Message----- > From: Aaron Brady [mailto:castironpi@comcast.net] > Sent: Sunday, May 13, 2007 9:28 PM > > > -----Original Message----- > > From: python-ideas-bounces(a)python.org [mailto:python-ideas- > > bounces(a)python.org] On Behalf Of Aaron Brady > > > > class GuardDefault: > > Val= object() > > def __call__( self, *args, **kwargs ): > > args=list(args) > > for i,j in enumerate( args ): > > if j is GuardDefault.Val: > > offset= > > self.callable.func_code.co_argcount-\ > > len(self.callable.func_defaults) > > args[i]= > > self.callable.func_defaults[i-offset] > > return self.callable( *args,**kwargs ) > > def __init__( self,callable ): > > self.callable= callable > > Do you have any interest in pursuing this? Actually not too bad for functools. Does this take a proposal? -I- am God-awful at lengthy technical writing.

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Function/method call issues
by Raj B May 14, 2007

May 14, 2007

Hello everyone, First of all, I'll introduce myself. I've been working on a Python compiler written in OCaml for about a year now. Some of you might know me from my talk at Google. One of the list members suggested this mailing list as a good forum for discussion and bouncing ideas. I think that one issue to consider are the complex semantics of functions and method calls. Whenever a function call is made, there is a lot of checking involved as to 'where' the function is called from: i.e. whether it's a user-defined function/method, a built-in function/method, a class function/method or an instance function/ method. Just reading the reference manual section on 'function objects' is enough to see how many different cases are there. Of course, this provides tons of flexibility in reusing the same code for different ways. However, it increases the amount of book-keeping and pre-processing required for a call. For example, Consider an object that implements methods 'str' and 'append' (the list object, for instance). During retrieval of methods, the following default retrieval method is called (in OCaml syntax, a simplified version). let list_getattr o attr = let v = get o.dict attr in (* lookup the attribute in the dictionary *) match attr with | String "append" | ... | -> v.instance = o; v (* set the method's instance to o before returning it *) | _ -> v (* else return the method object as is *) So basically, I have to check for two cases based on the actual names of the methods being called. This seems like extra work for the runtime. As a suggestion, I think that adopting a single calling convention (either 'x.foo()' or 'foo(x)') would have 2 advantages. 1) It would make it easier for users and make for more readable code. I still find myself having to refer to the docs to find out how a method needs to be called. 2) It would improve performance by reducing these checks shown above to one case. What do y'all think? Would this sacrifice too much flexibility? If this topic has been discussed on this list before, please feel free to point me there. Thank you Raj

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python appreciation site
by Aaron Brady May 13, 2007

May 13, 2007

This is a joke, for austerity. http://home.comcast.net/~castironpi/pythonappr.html

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parameter omit
by Aaron Brady May 13, 2007

May 13, 2007

Is it possible to signal to a parameter to use its default? def f( a, b=None, c='' ):... f( 123, <def>, 'abc' ) f( 123, ObjA, <def> ) Did I miss something, plus did you cover it before?

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Re: [Python-ideas] parameter omit
by Tal Einat May 13, 2007

May 13, 2007

On 5/11/07, Aaron Brady <castironpi(a)comcast.net> wrote: > > > > Perhaps we could learn from experience? > > > > I've recently had to automate Excel with Python and used the COM > > interface. In COM, there is a value called "Missing" which is passed to > > functions when no value should be passed for an argument - similar to > your > > DefaultArg. This leads to code like this (C# code examples): > > > > http://msdn2.microsoft.com/en-us/library/aa168343(office.11).aspx > > (straight from the online MSDN) > > > > MenuBarItem = MainMenuBar.Controls.Add( > > Office.MsoControlType.msoControlPopup, > > Type.Missing, Type.Missing, Type.Missing, true); > > > > And that was not a far-fetched example - here is an extreme example: > > > > http://blogs.ittoolbox.com/visualbasic/evolution/archives/importing- > > unformatted-excel-sheets-into-sql-server-2000-using-net-part-i-7501 > > <http://blogs.ittoolbox.com/visualbasic/evolution/archives/importing- > > unformatted-excel-sheets-into-sql-server-2000-using-net-part-i-7501> > > > > Excel.Application excelApp = new Excel.ApplicationClass(); > > Excel.Workbook thisWorkbook = > > excelApp.Workbooks.Open(strFileName,Type.Missing, Type.Missing, > > Type.Missing, Type.Missing,Type.Missing, Type.Missing, Type.Missing, > > Type.Missing,Type.Missing, Type.Missing, Type.Missing, > > Type.Missing,Type.Missing, Type.Missing); > > > > > > IMO this is horrendous. Horrible. Eye-gouging. > > > > I'd rather write machine code in hex. > > > > > > - Tal > > Ok, this isn't working to get my idea over. There's something wrong with > somebody, and it's simplest to assume its me. Probably inexperience in > posting. Not to mention, I have no idea who I'm talking to, or what the > local dialect is. (Sorry about the blank message too... wrong keystroke.) > > Tal's examples don't contradict me. In his, I call: > > > MenuBarItem = MainMenuBar.Controls.Add( > > Office.MsoControlType.msoControlPopup, thenamedarg= true); > and > > Excel.Workbook thisWorkbook = excelApp.Workbooks.Open(strFileName) > > Traditional function call. Calls still will work the way they do today. > You have -extra- flexibility, not less, sir. I add zero requirements. > Please let me repeat. Nothing breaks. These are simply the examples I could find with several minutes of Googling, admittedly not great examples, as you pointed out. I was just trying to show real world ugly code which was written as a result of an infrastructure adopting a concept which is very similar to the one which you propose. The point was to show that adopting your suggestion could result in even less readable function calls. Yes, nothing breaks. I really get it. I'm against this because it is, IMHO, not Pythonic. I'm not saying it won't be possible to write readable code. I'm saying it -would- be possible to write even less readable code. Specifically, I might be forced to write such ugly function calls when calling functions written by others, therefore adopting this feature could lead to my being forced to write uglier code. Not to mention reading others' uglier code... - Tal (P.S. in the first example, a keyword argument could not be used, because all of the arguments were positional.)

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Re: [Python-ideas] parameter omit
by Josiah Carlson May 13, 2007

May 13, 2007

"Aaron Brady" <castironpi(a)comcast.net> wrote: > > From: Josiah Carlson [mailto:jcarlson@uci.edu] > > "Aaron Brady" <castironpi(a)comcast.net> wrote: > > > What is the default parameter for the function? Problem is, the docs > > don't > > > say what it is. Does it pick its own filename to use for empty inputs? > > > > >>> import urllib > > >>> help(urllib.urlretrieve) > > Help on function urlretrieve in module urllib: > > > > urlretrieve(url, filename=None, reporthook=None, data=None) > > > > >>> > > No nitpicking, Mr. Carlson. These pieces of information are -not- always > available. Should I send you my 486 laptop so that you can have access to a Python interpreter? Because I really can't see how you being ignorant of the arguments to a standard library function in any way supports your case. Further, if you always use 'None' as the default for functions being called, then you can get things like this... class WebRetrieveElement: hook = None filename = None def netretrieveNew( self ): filename= self.filename or ParamDefault hook= hasattr( self,'hook' ) and self.hook or ParamDefault urlretrieve( self.url, filename, hook ) def netretrieveBest(self): urlretrieve(self.url, self.filename, self.hook) And look at that. I define two class level variables and all of a sudden the implementation of netretrieveBest gets a trivial implementation (though it breaks netretrieveNew, which uses a generally frowned upon mechanism that fails when filename and hook are None). But no, lets add a completely useless instance of object so that people can pass silly default arguments like ParamDefault that is a bazillion times more confusing than what Python users have been using for 15 years; None. - Josiah

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Re: [Python-ideas] parser in stdlib
by Adam Atlas May 13, 2007

May 13, 2007

On 10 May 2007, at 18.39, Aaron Brady wrote: > There is, but I want access to it. >>>> import parser >>>> parser.__file__ > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > AttributeError: 'module' object has no attribute '__file__' That's because it's a builtin module, written in C. It's Python/ parsermodule.c in the source distributions. What exactly are you suggesting should be possible? Are you trying to programmatically change the parser?

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