🌐 Mailman 3 September 1999 - Python-list - python.org

Memory leak in JPython beta 2
by Serial # 19781010 Oct. 5, 1999

Oct. 5, 1999

I run the following program for about 200+ iterations and see a pretty reasonable memory leak; after 800 passes, the leak is large. Has anyone else seen this with the beta2 version? Does the new beta 3 version fix the (at least apparent) memory leak? I'm running JDK 1.1.7 on HP-UX 10.20. This is a serious problem for us as we want to use JPython to translate XML formats for a large number of messages. === justInterp.py === def execute(): return === justInterp.java === import com.sun.xml.tree.*; import org.w3c.dom.*; class justInterp { public static void main(String [] args) { String script = "justInterp.py"; for (int i = 0; i < 100000; i++) { System.out.println("Executing execute() for the " + i + "th time"); org.python.util.PythonInterpreter interp = new org.python.util.PythonInterpreter(); interp.execfile(script); interp.exec("execute()"); interp = null; System.gc(); try { Thread.sleep(500); } catch (Exception e) { } } } } === end files === Thanks and have fun! - Bob

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mxODBC and NT services
by damien_morton＠my-deja.com Oct. 5, 1999

Oct. 5, 1999

hi people, Im about to embark on something on an adventure in Python programming - the creation of an SMTP server that uses a database to store incoming and outgoing emails. All of the SMTP severs I have examined store incoming and outgoing emails as files in spool directories. For extremely large numbers of emails (50k+), this will bring an OS to its knees. A database, on the other hand, will cope just fine (at least, thats my theory). Before I embarked on this project, I thought Id post a note to see if anyone had any comments, suggestions, or warnings about the use of the mxODBC drivers, and about my project in general. I intend using the mxODBC drivers in a fairly heavily multithreaded environment under Windows NT - i.e. in an NT service. Most of the outgoing emails will be generated on demand as lists are processed, so, in truth, there wont be massive volumes of data being transferred over ODBC. This thing will have to be pretty damned reliable though. I have read that ODBC has certain limitations when running as an NT service of with threads. Do anyone think this will be a problem at all? Does anyone have any experince with this that they might share? Ive listed the relevant MS KB artiles below. Ive read them and think that the problems is probably much more minor than I imagine. Limitations of DAO, DAO SDK in NT Service or with Threads http://support.microsoft.com/support/kb/articles/Q156/1/38.asp Running ODBC Applications as Windows NT Services http://support.microsoft.com/support/kb/articles/Q136/4/81.ASP Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.

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Last question of the day (This one's easy!)
by Nolan Darilek Oct. 5, 1999

Oct. 5, 1999

Ok. I'll try to refrain from asking any other newbiish questions for awhile and let everyone recover. This one's much easier than my last one. Promise! :) As I'm sure several of you remember, I'm working on a MUD server in Python. Yesterday, when I was somewhat naive about how difficult it would be to implement a distributed server (That idea's been scratched, BTW.) one of my concerns was the speed of an interpretted language for this task. My initial argument for doing this project in an interpretted language vs. a traditional language was flexibility; I wanted the ability to drastically change the system without having to recompile, messing with dynamic loading, etc. I also reasoned that MUDs have been using interpretted languages for years. For example, LPMUD uses LPC, in which most of the MUD environment is written. (Though, admittedly, I know very little about this codebase, since it usually isn't used to build the type of game which I want.) Initially, I thought that if a MUD server could be written in Java (http://www.twistedmatrix.com) a Python version would be smaller, easily readable, etc. Now, however, I'm becoming concerned about how possible/practical this would be, and if I'm possibly using Python for something for which it isn't intended. I began doing research into Python's speed vs. Java, and had some concerns. I don't like to pose questions to newsgroups without doing some small level of research first. So, I started by reading the Java vs. Python analysis at http://www.python.org/~rmasse/papers/java-python96/. I read most of the paper, simply to have a little more firepower to throw around in any Python vs. Java religious wars which I may be involved in. :) What interested me, though, was the paper's comparison between Java's and C's respective runtime speeds. The paper included the following code to illustrate its point that Java code ran slower than similar C code: import java.util.Date; class BenchMark { public static void main (String argv[]) { System.out.println("Start Time: " + new Date().toString()); int i; Nothing bar; bar = new Nothing(); for (i = 0; i < 100000000; i++) bar.foo(); System.out.println("End Time: " + new Date().toString()); } } class Nothing { public static void foo () { return; } } I know that interpretted code is slower than compiled code; that isn't my concern. I did, however, write the following (Equivilant?) benchmark in Python: #!/usr/bin/python import time def foo(): return "" print time.ctime(time.time()) x = 1 while x <= 100000000: foo() x = x+1 print time.ctime(time.time()) Running the compiled Java code produces the following on my PPro 200: ethereal:~> java BenchMark Start Time: Thu Sep 30 17:53:00 CDT 1999 End Time: Thu Sep 30 17:53:41 CDT 1999 So we see that it takes roughly 41 seconds to loop through 100000000 method calls. Not bad. I ran py_compile on the Python module though, and here's what I get: ethereal:~> python test.pyc Thu Sep 30 17:56:53 1999 It is now almost 5:59, and the task is still running. So, it looks as if Python is much slower at this particular benchmark than Java. My first question is, should I even care? Since my program isn't going to repeatedly call 100000000 methods in a loop, should the fact that Python is slower at it concern me? I'm sure that there are other benchmarks, and some are more accurate than this little "poor man's benchmark" which I chose to run. Second, is there a way to speed up the above Python benchmark script? Am I doing something which is hindering its execution? Again, I did compile to bytecode, which sped up earlier tests greatly. Finally, and this is the question to which I'm almost afraid to see the answer . . . Is Python appropriate for this task? I learned Python almost a year ago, but have only recently worked with it extensively, and I really enjoy it. When I saw the Twisted Reality MUD server (see above URL) written in Java, I thought that it would be great to implement my ideas in an interpretted language. There are some features of Java which annoy me though, and I would very much like to do this in Python. Should I just continue scaling up my work and testing it, determining how the various components function and optimizing them if necessary? Or, should I seriously consider reimplementing my project in another language? Whew! That was a long QOTD, but one of my last for awhile, unless I need to comment on this one. :) Please understand; I'm not trying to initiate a religious/flamewar. I have some experience with embedding Python in other applications and extending it with additional functionality, but I've never developed a serious server application, and I've never really been concerned about runtime speed. So hopefully I won't start World War III. :) And, just as an aside, it is now 6:09 and the Python benchmark is still running. Hopefully I'm just blowing things way out of proportion, and I've gone about testing speeds in the completely wrong way. If you've read this far, thanks a bunch! :)

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Python guide Brain posted
by T. C. Mits Oct. 5, 1999

Oct. 5, 1999

FYI: I created an initial version of a guide to the Python language using Natrificial's TheBrain technology. Its posted to their ThinkTank (a database of user created Brains) at: <http://brainserver.thebrain.com/get.asp?i=3f51b> I won't quote what the Brain is and all that (see www.theBrain.com); it may appear I'm directly advocating something or spamming. Anyway, I think its pretty usable, especially for Python Newbies, like me. Any suggestions on its layout would be appreciated. Unfortunately, a 'guide' Brain in contrast to a web hosted 'Web Site' Brain, requires Windows and a two meg download for a trial version of the client which doesn't overwrite DLLs!). They state that other platforms, like Unix and palm computers, are under development. Me.

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system resource modules? (Win32, Irix)
by Sean Dunn Oct. 5, 1999

Oct. 5, 1999

Are there any pre-coded system resource modules for Win32 and/or Irix? I have looked everywhere, and have started coding my own - but I want to avoid RTW... Basically, I need max physical memory, free physical memory, total virtual, free virtual... so far. And any other goodies that are cross-platform. Sean

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Circular refs
by Adrian Eyre Oct. 5, 1999

Oct. 5, 1999

Is there a reasonable fix for this? >>> class Noisy: ... def __init__(self, name): ... self._name = name ... print "Created " + self._name ... def __del__(self): ... print "Destroyed " + self._name ... >>> a = Noisy("a") Created a >>> b = Noisy("b") Created b >>> del a Destroyed a >>> del b Destroyed b Fair enough, but... >>> a = Noisy("a") Created a >>> b = Noisy("b") Created b >>> a.b = b >>> b.a = a >>> del a >>> del b [Sound of memory dripping onto the floor] -------------------------------------------- Adrian Eyre <mailto:a.eyre@optichrome.com> Optichrome Computer Solutions Ltd Maybury Road, Woking, Surrey, GU21 5HX, UK Tel: +44 1483 740 233 Fax: +44 1483 760 644 http://www.optichrome.com --------------------------------------------

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More Python books coming...
by Guido van Rossum Oct. 5, 1999

Oct. 5, 1999

I did a search for Python on Amazon.com and found several new Python books that are likely to hit the shelves soon. Here's the list: The Quick Python Book Daryl Harms, Kenneth McDonald. Published by Manning Publications. Expected September 1999. Python Essential Reference David Beazley. With a foreword by Guido van Rossum. Published by New Riders. Expected October 1999. Programming with Python Tim Altom. Published by Prima Publishing. Expected October 20, 1999. Python and Tkinter Programming John E. Grayson. Published by Manning Publications. Expected November 1999. Python Annotated Archives Martin Brown. Published by McGraw-Hill. Expected September 1999. Python Programming on Win 32 Mark Hammond, Andy Robinson. Published by O'Reilly. Expected September 1999. Sams Teach Yourself Python in 24 Hours Ivan Van Laningham. Published by Sams. Expected November 1999. We expect to have a bookstand at the Python conference in January where you can buy these and other Python books. I've also added this to http://www.python.org/doc/Books.html. --Guido van Rossum (home page: http://www.python.org/~guido/)

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Moving from Perl to Python
by Thomas Weholt Oct. 4, 1999

Oct. 4, 1999

Hi, I got some experience in Perl, but want to move over to Python for several reasons. One is discussed in an earlier thread, another is the fact that I`m having a hard time understanding effective perl-scripts due to the syntax. Python seem better, ie. easier to read. I got almost every book available on Perl published by O`reilly and one of them, The Perl Cookbook, stands out as the most helpful. I was wondering if there were any other book or document online available for Python? It has the structure of a simple question or desription of a common task and code examples + explanation on how to solve it. Another thing that could help was if there was a document describing how to migrate from Perl to Python, with examples. PS ! I`m using hashes and modules in Perl, like MLDBM and MP3Info, are there any similar modules for Python? I know Python can read hash-tables created with the DB_File-module, but can it read/write files created with the MLDBM-module? If this mail is incomprehensible etc. I`m sorry. I was in a hurry. Thanks anyway. Thomas Weholt, Norway

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When Good Regular Expressions Go Bad
by Douglas Alan Oct. 4, 1999

Oct. 4, 1999

I'm probably just out of luck (i.e., I can't find any mention of it in the FM), but just in case, I'll ask anyway. It seems to me that even when a regular expression fails to match a string, you might want to know just how far it was able to get before getting stuck. (And indeed I do!) For instance, let's say that I have the regular expression "^foo.bar", and I try to match it on the string "fooxbaz". It might be useful to be able to find out that the regular expression was able to get all the way through "fooxb" before giving up the ghost. Now, perhaps what I am asking for doesn't make much sense for regular expressions that involve backtracking, but in this case some response could still be provided -- perhaps, for instance, the longest string that was partially matched. Or, a bit less usefully, just the last location where it got stuck. |>oug

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Matching templates against a tree - any ideas?
by Ian Clarke Oct. 3, 1999

Oct. 3, 1999

This isn't a Python question, but I would imagine that it might appeal to the type of people who frequent this list. While recently thinking of good ways to automatically solve equations, I came across the problem of trying to find an efficient method to match a tree, or subtree of that tree, against a template - so that a transformation could be applied. Lets say that I defined a transformation (expressed in Polish notation) as such: *+AB+CD -> ++*AC*AD+*BC*BD This represents: (A+B)*(C+D) -> (A*C)+(A*D)+(B*C)+(B*D) Now lets say I had an expression, say: ++m*++mkp+f*nkf The tree for this looks like: + / \ + f / \ / \ m * / \ / \ + \ / \ \ / \ + + p / \ / \ f * m k / \ n k Can I apply the transformation given above to this equation? In fact I can, the segment *++mkp+f*nk matches the template, where: A=+mk B=p C=f D=*nk The obvious algorithm for this is to traverse the tree attempting to match each subtree in the tree against the template, however this would be inefficient (there could be many trees, each if which may be large, and many templates). But I need an efficient algorithm for performing that match. Anyone got any ideas? Ian. -- "Don't throw your PC out the window, throw Windows out of your PC, and install Linux" Ian Clarke http://www.gnu.demon.co.uk/

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