🌐 Mailman 3 February 2000 - Python-list - python.org

Multi-argument append() is illegal
by Guido van Rossum March 27, 2000

March 27, 2000

I've noticed that there is some code out there that creates a list of tuples and uses code like list.append(a,b,c) to add the tuple (a,b,c) to the list. According to the documentation, this is illegal: append() only takes a single argument, and one should write list.append((a,b,c)). However, the actual append() implementation didn't mind, and implemented list.append(a,b,c) as list.append((a,b,c)). Many people are using this even though it's never been documented. I am going to rectify this in Python 1.6 -- people coming from other languages might well expect list.append(a, b, c) to mean the same as list.append(a); list.append(b); list.append(c), and it's always been my philosophy to make ambiguous syntax illegal rather than to pick one interpretation randomly. This message is simply a heads-up that you should be aware of this change (when 1.6 comes out, which should be before the summer). You can test your programs using the current CVS version (see www.python.org/download/cvs.html). You can also grep through your sources for a pattern like "\. *append *\(.*," -- which doesn't find every occurrence, but is a good starting point. If you have a smarter grep-like tool you may be able to write a tighter matching expression. Watch out for false hits though: some classes define their own multi-argument append()... --Guido van Rossum (home page: http://www.python.org/~guido/)

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Is mxDateTime compatible with Installer
by Calishar March 15, 2000

March 15, 2000

Hi Folks, I'm asking this question because I just added mxDateTime support to an application which was already working, but needed much better date handling. Since then, any time I try to use the Installer Package (most recent version as of monday last week) the final application fails with import errors. At first it was failing saying it "couldn't import name __version__" in the __init__.py files in the DateTime directory and the mxDateTime subdirectories. I modified the __init__ files to set the version (1.3.0) rather than importing it, okay, got past that point. Now I am getting the following message. File "C:\Program Files\Python\Lib\DateTime\DateTime.py", line 12, in ? NameError: DateTimeDelta Line 12 in the DateTime.py file sets the value oneSecond. I am currently using Python 1.5.2 (downloaded maybe 2 months ago at the most), win32all-128, mxDateTime 1.3.0 on a windows 95 development system at the office, Win98 at home, and a Win95 test system. Any ideas on what is happening or how to fix it? Calishar

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Tkinter: creating a scrolling canvas that contains widows (Frame widgets)
by Kevin Cazabon March 15, 2000

March 15, 2000

I've been trying to create a class that I can use to place Frame() widgets into a scrolling 'container'. Basically, I want a master "Frame" that has a Y scroll bar (and maybe X as well). In this frame, I want to be able to add sub-frames (any number). If all of these frames won't fit, I want to be able to scroll the master Frame as necessary. The only suitable Tkinter class for the Master I can find is the Canvas widget. I have no problem creating this, and adding windows to it using canvas.create_window(x,y, window=mywidget), but have had a heck of a time getting it to scroll properly, especially when the user resizes the overall master frame. This may sound complicated, but it really isn't... just the implementation might be! Any suggestions, or if you can point me to an exapmle that might help (like the ScrolledText widget, which is very similar to what I need, kindof...), I would greatly appreciate it. Kevin Cazabon kcazabon(a)home.com

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Wash. D.C. Area: DCPIGgies, Mar. 13
by Jeremy Hylton March 14, 2000

March 14, 2000

Notice to all Washington DC area Python users: We will be having our first DCPIGgies (DC Python Interest Group) meeting of the year on Monday March 13, 2000 from 7:30pm to 9:00pm at CNRI in Reston, Va. Speaker: Scott Cotton Static Type and Interface Checking for Python General Review and Fundamental Decisions Abstract ---------- This presentation reviews various possible ways of adding static type checking to python. The problem poses two questions: 1) What sort of static type checking system would be most appropriate for python? 2) By what means may static type checking be made optional? A decision tree for each question is presented based on a combination of type theory, an understanding of python, and properties that have become apparent in the development of a sample type checking system. Finally, we discuss some overall approaches that would maximize the benefits and/or minimize the drawbacks of adding optional static type checking to python. Scott will be speaking from 8:00 to 9:00pm. We will have food and introductions starting at 7:30pm. We may also have some time after the talk for Q&A with Guido and Barry on Python and JPython. Pizza, salad, and soda will be provided courtesy of Foretec Seminars. Please RSVP by email to jeremy(a)cnri.reston.va.us. I need to know how many people will attend and how many will be eating pizza. Directions to CNRI can be found on the Web: http://www.cnri.reston.va.us/directions.html Mailing list: There is a mailing list for people interested in DCPIGgies meetings; see http://www.python.org/mailman/listinfo/dcpiggies. This is a low volume list for announcing meetings, arranging to share rides, and other thrilling PIGgy topics. See you there! Jeremy

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Hotfolder class
by Pieter Claerhout March 11, 2000

March 11, 2000

Does anyone has a class which can be used for a hot folder mechanism? (You know, when you drop a file in a folder, that you can pick it up and do something with it) Thanks, <P>

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Re: functional programming
by François Pinard March 10, 2000

March 10, 2000

Moshe Zadka <moshez(a)math.huji.ac.il> écrit: > > using Python.My guess is that I would have no problem naming my lambda's > > (using `def'), and approximating lexical closures (using `class'). > > > > Maybe we should not get distracted that much by syntactical sugar! :-) > You can't do serious functional programming without tail recursion. I could iterate explicitly and easily, which is not a bad thing anyway. Tail recursion is good for many things, it can be used to hint optimising compilers, yet past a certain point, we start loosing legibility. For me, functional programming is a way of writing algorithms in which you have an important stress on functions as primary objects, dynamically building functions from more elementary ones, inter-relating functions, and often using them to represent partial solutions. It is not defined as abusing of function calls, or avoiding assignment or iteration. I may be all wrong, but I think functional programming is more an approach to solving problems, than a code writing style. -- François Pinard http://www.iro.umontreal.ca/~pinard

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IDLE Icon Name
by Randall Hopper March 10, 2000

March 10, 2000

If you set the title of the IDLE window: idle.py -t IDLE It works, but why does the icon name come up as "*IDLE" rather than "IDLE"? -- Randall Hopper aa8vb(a)yahoo.com

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Making sense of Stackless
by Darrell March 9, 2000

March 9, 2000

Thinking about how I could use Stackless and how it's different from using callbacks on a object. I decided to view continuations as objects and here's were it lead. If an instance can be thought of as a stack frame then a continuation can be thought of as an instance with a constructor and a run method. import continuation def construct(): tripFlag=1 c=continuation.caller() tf=c.update(tripFlag) if tripFlag==1: # Don't understand how tripFlag stops being equal to 1 return c return tripFlag def classFunc(): print 'Construct:' x=1 y=2 c=construct() if c != None: return c else: print 'Run:' x=x+1 print x+y c=classFunc() for x in range(3): c.call() print '#'*20 def classIterator(seq): offset= -1 c=construct() if c != None: return c else: offset=offset+1 return seq[offset] c=classIterator(range(10)) for x in range(3): print c.call() #################### #Now Python has a class with truly private data. #Unless Christian has a trick. Construct: Run: 4 Run: 5 Run: 6 #################### 0 1 2 --Darrell

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Re: perl chomp equivalent in python?
by François Pinard March 8, 2000

March 8, 2000

"a.c.a. serier" <a.serier(a)hccnet.nl> writes: > Perl has chomp() to do this. To chop (even if line is truly empty): line = line[:-1] To chomp: if line and line[-1] == '\n': line = line[:-1] You may remove the test for line if you know that it is not empty. -- François Pinard http://www.iro.umontreal.ca/~pinard

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modules documentation
by Xose L. Gonzalez March 8, 2000

March 8, 2000

Hi Being new in Python, I got impressed by its easiness for learning it and using it, but IMO there is a lack of documentation, namely: Where (web page) can I get a modules' documentation more complete than the one supplied in the Python delivery, specially regarding the text files processing?? (normally there are no examples in the modules tutorial) As a general comment: really Python is fantastic, but the documentation is very importatn to demosntrate it. I think it is a common problem in softawre (my problem also): we do very good applications but we do not like at all doing documentation. PS: email copy of the answer would be appretiated. Thanx in add-vans

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