Mailman 3 November 2000 - Python-Dev

Re: [Python-Dev] installing IDLE & other Tools
by Moshe Zadka Nov. 16, 2000

Nov. 16, 2000

[Jeremy Hylton] > We've discussed installation of other tools once or twice, but I've > never decided what exactly to do. The compiler package, for example, > comes with a distutils setup.py script that will do the job. I think > the best way to move forward is to write setup.py scripts for all the > other tools that ought to be installed. That does seem reasonable. It seems the most non-intrusive, since we get out of the way of proffessional packages, while still giving them … [View More]

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Work in progress - coercion/cmp overhaul
by Neil Schemenauer Nov. 15, 2000

Nov. 15, 2000

[The python-dev list server seems to have gotten hungry and eaten my original message. I'm trying again.] I making this available now in the hope that it will generate some dicussion: http://arctrix.com/nas/python/coerce-2.diff The patch is based on Marc-Andre Lemburg's coercion patch for 1.5.1 downloaded from the starship: http://starship.python.net/~lemburg/CoercionProposal.html All credit goes to him. The bugs are probably introduced by me. What the patch does: - … [View More]

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Making popen2 actually work
by Eric S. Raymond Nov. 15, 2000

Nov. 15, 2000

OK, so Guido told me at one point that 2.0 was supposed to have included changes to the way buffering of I/O to subprocesses is handled. I've installed 2.0, and I need to know how to make the following program work: import os, sys (child_stdin, child_stdout) = os.popen2("/usr/bin/rev", "t", 1); print "* Child process spawned" while 1: line = raw_input(">"); child_stdin.write(line); child_stdin.flush() print "* Line written to child process" transformed = child_stdout.… [View More]

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statically nested scopes
by Jeremy Hylton Nov. 15, 2000

Nov. 15, 2000

Title: Statically Nested Scopes Author: Jeremy Hylton <jeremy(a)digicool.com> Status: Draft Type: Standards Track Created: 01-Nov-2000 Abstract This PEP proposes the additional of statically nested scoping (lexical scoping) for Python 2.1. The current language definition defines exactly three namespaces that are used to resolve names -- the local, global, and built-in namespaces. The addition of nested scopes would allow resolution of unbound local names in … [View More]enclosing functions' namespaces. One consequence of this change that will be most visible to Python programs is that lambda statements could reference variables in the namespaces where the lambda is defined. Currently, a lambda statement uses default arguments to explicitly creating bindings in the lambda's namespace. Notes This section describes several issues that will be fleshed out and addressed in the final draft of the PEP. Until that draft is ready, please direct comments to the author. This change has been proposed many times in the past. It has always been stymied by the possibility of creating cycles that could not be collected by Python's reference counting garbage collector. The additional of the cycle collector in Python 2.0 eliminates this concern. Guido once explained that his original reservation about nested scopes was a reaction to their overuse in Pascal. In large Pascal programs he was familiar with, block structure was overused as an organizing principle for the program, leading to hard-to-read code. Greg Ewing developed a proposal "Python Nested Lexical Scoping Enhancement" in Aug. 1999. It is available from http://www.cosc.canterbury.ac.nz/~greg/python/lexscope.html Michael Hudson's bytecodehacks projects at http://sourceforge.net/projects/bytecodehacks/ provides facilities to support nested scopes using the closure module. Examples: def make_adder(n): def adder(x): return x + n return adder add2 = make_adder(2) add2(5) == 7 from Tkinter import * root = Tk() Button(root, text="Click here", command = lambda : root.test.configure(text="...")) One controversial issue is whether it should be possible to modify the value of variables defined in an enclosing scope. One part of the issue is how to specify that an assignment in the local scope should reference to the definition of the variable in an enclosing scope. Assignment to a variable in the current scope creates a local variable in the scope. If the assignment is supposed to refer to a global variable, the global statement must be used to prevent a local name from being created. Presumably, another keyword would be required to specify "nearest enclosing scope." Guido is opposed to allow modifications (need to clarify exactly why). If you are modifying variables bound in enclosing scopes, you should be using a class, he says. The problem occurs only when a program attempts to rebind the name in the enclosing scope. A mutable object, e.g. a list or dictionary, can be modified by a reference in a nested scope; this is an obvious consequence of Python's reference semantics. The ability to change mutable objects leads to an inelegant workaround: If a program needs to rebind an immutable object, e.g. a number or tuple, store the object in a list and have all references to the object use this list: def bank_account(initial_balance): balance = [initial_balance] def deposit(amount): balance[0] = balance[0] + amount def withdraw(amount): balance[0] = balance[0] - amount return deposit, withdraw I would prefer for the language to support this style of programming directly rather than encouraging programs to use this somewhat obfuscated style. Of course, an instance would probably be clearer in this case. One implementation issue is how to represent the environment that stores variables that are referenced by nested scopes. One possibility is to add a pointer to each frame's statically enclosing frame and walk the chain of links each time a non-local variable is accessed. This implementation has some problems, because access to nonlocal variables is slow and causes garbage to accumulate unncessarily. Another possibility is to construct an environment for each function that provides access to only the non-local variables. This environment would be explicitly passed to nested functions. [View Less]

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Installing 2.0 seems to have broken Tkinter
by Eric S. Raymond Nov. 14, 2000

Nov. 14, 2000

I installed from the Beopen-Python-2.0 RPM at Source Forge. Now: golux:~/WWW/fetchmail$ fetchmailconf Traceback (most recent call last): File "./fetchmailconf", line 9, in ? from Tkinter import * File "/usr/local/lib/python2.0/lib-tk/Tkinter.py", line 35, in ? import _tkinter # If this fails your Python may not be configured for Tk ImportError: No module named _tkinter This is a serious problem. Is there a non-broken RPM out there? -- <a href="http://www.tuxedo.org/~esr/"&… [View More]

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Nested functions and class scope
by Guido van Rossum Nov. 14, 2000

Nov. 14, 2000

John Max Skaller wrote: > Guido van Rossum wrote: > ===============>>>> > > Other issues that need sorting out: > > > > x = 2 > > class C: > > x = 1 > > C = 'some string' > > def a(self): > > print x > > def b(self): > > global x > > x = 3 > > > > class D(C): > > C = 'some string' > > def a(self): > > C.a(self) > > print C > > > … [View More]> o = C() > > o.a() > > o.b() > > o.a() > > > > o = D() > > o.a() > > > > What would the output look like under your proposal ? > > This is a good point! If we considered the class as a nested scope > here, I think it might break too much code, plus it would allow a new > coding style where you could reference class variables without a self > or <classname> prefix. I don't like that prospect, so I'm in favor > for ruling this out. > <<<=================== > > You're missing the point. you can refer to class variables without > a prefix right now: > > class X: > x = 1 > y = x > > > It would be madness NOT to support lexically scoped nested classes > as well as functions. But note that these scopes only exist > when a class is executed, that is, when the class is defined. > This has NO impact on finding class variables from an instance. > > output of above from Vyper: > -------------------------------------------------------------- > Viperi 2.0.1 > Copyright Maxtal P/L, John Skaller, Australia, 1999 > >>>x = 2 > ...class C: > ... x = 1 > ... C = 'some string' > ... def a(self): > ... print x > ... def b(self): > ... global x > ... x = 3 > ... > >>>class D(C): > ... C = 'some string' > ... def a(self): > ... C.a(self) > ... print C > ... > >>>o = C() > ...o.a() > ...o.b() > ...o.a() > ... > 1 > 3 > >>>o = D() > ...o.a() > ... > Error Near line 4 > > Uncaught Python Exception at top level!! > .. Kind: Instance of AttributeError > .. Attributes: > args --> Cannot find attribute of "some string" "a" > > Traceback (innermost first) > File: <string> Line: 4 > <cannot get line from file> > File: <string> Line: 2 > <cannot get line from file> > > -- > John (Max) Skaller, mailto:skaller@maxtal.com.au > 10/1 Toxteth Rd Glebe NSW 2037 Australia voice: 61-2-9660-0850 > checkout Vyper http://Vyper.sourceforge.net > download Interscript http://Interscript.sourceforge.net Looks like you are missing the point. Of course I want to keep the class as a local scope *inside the class def*. But I need it out of the way when executing methods. The example code should print 2 # a() references global x, not C.x 3 # global x got set to three by b() 2 # C refers to global class C <class C ...> # ditto I agree that this is surprising. But I believe it would break too much code if we implemented your (simpler) scheme. --Guido van Rossum (home page: http://www.python.org/~guido/) [View Less]

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Re: [Python-checkins] CVS: python/nondist/peps pep-0042.txt,1.43,1.44
by Moshe Zadka Nov. 14, 2000

Nov. 14, 2000

On Mon, 13 Nov 2000, Guido van Rossum wrote: > + - Killing a thread from another thread. Or maybe sending a > + signal. Or maybe raising an asynchronous exception. > + > + http://sourceforge.net/bugs/?func=detailbug&bug_id=121115&group_id=5470 In general, killing threads in considered a bad idea. It is usually much better to design the application properly, and being aware that a thread doing nothing is not that big a deal. -- Moshe Zadka <moshez(a)… [View More]

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This Project Has Not Released Any Files
by Martin v. Loewis Nov. 14, 2000

Nov. 14, 2000

[Tim Peters] > From BeOpen.com's POV, so long as they were paying major bills, they > would rather have download traffic tickle their ad banners than SF's > ad banners. Even though this should have been clear to me all the time, stating it explicitly triggers alarms for me. I just checked, and it appears that Python 2.0 is not available for download via ftp. In particular, it is not available via ftp from ftp.python.org! If it was there, mirrors all over the world would pick it up … [View More]

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installing IDLE & other Tools
by Jeremy Hylton Nov. 14, 2000

Nov. 14, 2000

I just saw your note about whether IDLE was packaged with the Python RPMs. It isn't, nor is anything in the Tools directory. I did the simplest thing possible with the RPM and ran "make install". The RPM installs whatever is installed as a result of that. We've discussed installation of other tools once or twice, but I've never decided what exactly to do. The compiler package, for example, comes with a distutils setup.py script that will do the job. I think the best way to move forward is … [View More]

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Re: [Python-checkins] CVS: python/dist/src/Objects fileobject.c,2.91,2.92
by Trent Mick Nov. 13, 2000

Nov. 13, 2000

On Mon, Nov 13, 2000 at 11:48:25AM -0800, Guido van Rossum wrote: > Update of /cvsroot/python/python/dist/src/Objects > In directory slayer.i.sourceforge.net:/tmp/cvs-serv4689 > > Modified Files: > fileobject.c > Log Message: > Added _HAVE_BSDI and __APPLE__ to the list of platforms that require a > hack for TELL64()... Sounds like there's something else going on > really. Does anybody have a clue I can buy? Yes, there is. For all of these platforms … [View More]

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