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

Re: Are decorators really that different from metaclasses...
by Hallvard B Furuseth Sept. 3, 2004

Sept. 3, 2004

Paul Morrow wrote: >Hallvard B Furuseth wrote: >>Paul Morrow wrote: >>> >>>I believe that we should think of assignments to __xxx__ attributes as >>>not being part of the function's body, but instead part of its >>>declaration, just as we do with its docstring. >>> >>> def circum(diameter): >>> """This describe's foo.""" >>> __author__ = 'Paul Morrow' >>> __version__ = '0.1' >>> __features__ = synchronized, memoized >> >> >> I really, really don't like this idea. Assignment in Python has quite >> enough pitfalls already. Please don't make it worse. If it looks like >> an assignment to a local variable, it should be an assignment to a local >> variable. > > Actually, these look like assignments to local *magic* variables. > There's the difference. No, that's not the difference. It's still different from how magic variables behave in all other places. (Class bodies, module bodies, object attributes). The difference is that magic variables in this particular localtion is actually parsed differently from use of variables other places, so the '=' operator (and what other operators?) means something else. > The double underscores before and after each name loudly proclaims > that these variables are not like 'normal' variables. They're special > in some way. No other magic variables are that special. They all behave normally _as variables_. Other parts of Python react to them being set or reset, the very variable assigments are quite normal. Except for the name mangling of __*__ instance variables, but that is a lot smaller exception than changing the namespace of the assignment operator and the time at which that operator is executed. >> If we are going to invent a syntax for declaring function >> attributes inside the function, why confuse the issue by making it look >> like it does something else? > > Because 1) adding new syntax should be resisted as much as possible > (IMO), If one can extend old syntax in an intuitive way, it's fine to reuse old syntax. When you extend old syntax to mean something counterintuitive, it's far better to find a new syntax. And while it may seem intuitive to you, you may have noticed that it seems counterintuitive to a lot of others. > and 2) this style has parallels in both class definitions and > module definitions. It parallels them as long as you don't think of how it works. Once you do think of how it works, it's completely different. And you get a lot of subtle differences to confuse the issue. > Compare this class statement with the function def > above. > > class Oval(Circle): > """This describe's Oval.""" > __author__ = 'Paul Morrow' > __version__ = '0.1' > __metaclass__ = M Yes, I can compare that. It's fine in a class body, which is executed when the class definition is executed. When I see it in a function definition, I see a strange use of the assignment operator, which is normally a 'run-time' operator, in a place where it not being executed at run-time. You keep displaying such examples as if they should make your point self-evident. Already several people have pointed out that they don't see it at self-evident. That might give you a clue that it isn't self-evident. >> It's true that it makes it look more like what __*__ attribute >> assignment in class bodies does, but the simple fact is that class >> bodies are executed when the class statement is executed, and function >> bodies are not executed when the def statement is executed. Now you >> want part of the function bodies to be executed at def time, and part at >> call time. > > Maybe we just need to be clear as to which lines under the def statement > constitute the function's /body/. That's perfectly clear without your change. Your change is confusing the issue, by also using an operator which one (well, at least many of us - not you, obviously) expects to be executed in the function body. > The function's docstring gets > assigned during processing of the def statement, therefore the docstring > is apparently not part of the function body; The function's doc string doesn't look like a statement, and even if it one thinks it is one (which documentation handling somehow picks out specially) it would be a no-op inside the function, so there is nothing confusing about it. BTW, I was all for having the function body extend further down - my first decorator choice (before J2) would have been the def foo(...): ...decorators and doc string... some_keyword: ...body... syntax. Like you point out about __*__ assigments it stands out, but it's even clearer, but it doesn't look like it would normally dosomething else, so the uninitiated will have far less reason to wonder what kind of voodoo is going on to make it do what it does. > So why not have assignments to __xxx__ > variables also be part of the function's declaration. Because it looks confusing. > The distinctive appearance of these names helps remind us that they > have special semantics. And if we use another syntax, we won't need to be reminded about anything, and there is nothing to be confused about. >> __*__ assigments in class bodies can look a little confusing if you >> don't think of how class declarations work, but it's perfectly simple >> once you think of how they do work: (...) > > Perhaps its just my experience with declarative programming languages, > but I prefer thinking of __xxx__ assignments in a class as setting > 'properties' of the class. (...) I prefer to try to think a bit like the language I'm using does. At least for me it makes it far easier to keep things straight. -- Hallvard

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Re: allowing braces around suites
by Kjetil Torgrim Homme Sept. 3, 2004

Sept. 3, 2004

[Andrew Durdin]: > > The whole topic of explicit[*] end-of-block markers was brought up > and discussed at great length in May 1994: > > http://groups.google.com/groups?threadm=9405061919.AA03028%40vicorp.com thank you for the reference! I'm happy to see that Guido wasn't strictly opposed to such a feature 10 years ago. > Regardless of history, it looks to me like your problem could be > better solved by modifying your emacs mode to consider whitespace > more correctly -- AFAICT there is no reason why it should ever > pick up the logging line in your example and indent it to the same > level as the else: block. how can Emacs tell? if I press TAB and thus ask Emacs to re-indent the line, that's what it will do. arguably, the correct fix is to disable the "clever" re-indentation code of Emacs since it's too easy to fool it, but this makes coding more awkward in other cases. it also doesn't solve cut-n-paste errors. -- Kjetil T.

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sys.stdin.readline()
by maxwell＠ldc.upenn.edu Sept. 3, 2004

Sept. 3, 2004

When I invoke readline() in a for loop, why does it return a series of one-char strings, rather than the full line? >>> for sL in sys.stdin.readline(): print sL ... abc a b c (I typed in 'abc', and the loop printed out 'a\nb\nc\n') I.e. how can I make readline() wait for the newline before returning a value? 'readline()' seems to be acting exactly like 'read()' here. ('readlines()' works fine in this context, except that it waits for eof; I'd really rather iterate over lines in stdin as they come in)

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Re: Announcing PyCs, a new Python-like language on .Net
by dw-google.com＠botanicus.net Sept. 3, 2004

Sept. 3, 2004

Mark Hahn <mark(a)prothon.org> wrote in message news:<mailman.2572.1093751093.5135.python-list(a)python.org>... > Please join the PyCs team. The only effort involved is particpating in a > low-traffic, high-content, mailing list. You will be able to influence the > design of the latest and greatest dynamic language. Hi there. What are you trying to achieve? You have yet to complete Prothon or even stabilise it for long enough to let me get a good overview of it. Might I suggest you take a step back and actually think about what you are doing rather than just implementing whatever happens to be considered cool today. Also judging by what I've seen of Prothon and read here, neither of your proposed languages are either Python-like or related to this group. Might I suggest you sit down with a paper and a pen and work out what problem you are actually trying to solve, it is starting to get rather embarrassing to watch the antics here. At the very least could you spell check your postings before sending them. There are also much better forums to discuss language development on than comp.lang.python. Sorry for the flame, but you really need it. David.

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initializing mutable class attributes
by Dan Perl Sept. 3, 2004

Sept. 3, 2004

There is something with initializing mutable class attributes that I am struggling with. I'll use an example to explain: class Father: attr1=None # this is OK attr2=[ ] # this is wrong def foo(self, data): self.attr1=data self.attr2.append(data) The initialization of attr1 is obviously OK, all instances of Father redefine it in the method foo. But the initialization of attr2 is wrong because all the instances of Father end up sharing the same value. Maybe that is desired sometimes, but usually it is just a bug. So the only solution I see to this is to initialize attr2 in __init__: class Father: attr1=None def __init__(self): self.attr2=[ ] This is already awkward because there is such a difference between attr1 and attr2. But moreover, I think this forces subclasses of Father to do something like this: class Child (Father): def __init__(self): Father.__init__(self) self.attr3=[ ] I find this even more awkward because many people will forget to do it. Clearly, this is then a more general issue with __init__, but I think it is accentuated by the fact that you HAVE TO HAVE __init__ in order to initialize attributes that are mutable. Is there something I don't know here and there is a better way to do this in Python? I would like to get a better solution or otherwise start a discussion.

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Re: "Content-Length" header
by Justin Sept. 2, 2004

Sept. 2, 2004

URL open appears to not want to work unless its paramater is an actual string spelled out in quotes. Check out the output to this code. When I give urlopen objects instead of pre strings it doens't work correctly. print linklisttype for y in linklisttype: temp = urlopen(y) print temp temp2 = temp.info() print temp2 temp3 = temp2.getheader("Content-Length") print temp3 file_sizes.append(temp3) print file_sizes #This is the tuple with three urls in it, they all look correct to me ['http://www.ecs.soton.ac.uk/~harnad/temp/ariadne-rae.doc', 'http://www.ecs.soto n.ac.uk/~harnad/temp/ukparl.doc', 'http://www-admn.csun.edu/systech/techsupport/ procedures/2kcleanup.doc'] #here are the return values for y =0, didn't work <addinfourl at 25805248 whose fp = <socket._fileobject object at 0x014093B0>> Date: Mon, 30 Aug 2004 21:10:50 GMT Server: Apache/1.3.27 (Unix) (Red-Hat/Linux) mod_ssl/2.8.12 OpenSSL/0.9.6b DAV/ 1.0.3 PHP/4.3.2 mod_perl/1.26 Connection: close Content-Type: text/html; charset=iso-8859-1 None #same here <addinfourl at 25805048 whose fp = <socket._fileobject object at 0x01409688>> Date: Mon, 30 Aug 2004 21:10:53 GMT Server: Apache/1.3.27 (Unix) (Red-Hat/Linux) mod_ssl/2.8.12 OpenSSL/0.9.6b DAV/ 1.0.3 PHP/4.3.2 mod_perl/1.26 Connection: close Content-Type: text/html; charset=iso-8859-1 None #this one worked though i don't know why. If I paste the URLs they all work <addinfourl at 25807968 whose fp = <socket._fileobject object at 0x01409650>> Server: NetWare-Enterprise-Web-Server/5.1 Date: Mon, 30 Aug 2004 21:10:53 GMT Content-type: application/msword Last-modified: Tue, 30 Apr 2002 22:50:08 GMT Content-length: 297984 Accept-ranges: bytes Connection: close 297984 [None, None, '297984']

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Installation of mod_python 3.1.3 on Apache 2.0.50 on Windows Me/Win2k
by pit.grinja＠gmx.de Sept. 2, 2004

Sept. 2, 2004

Hi there, I cannot install mod_python v3.1.3 on either Win2k/ActivePython 2.3.2 or WinMe/Python 2.3.4. When I run the Windows installer, I get the following error message: Traceback (most recent call last): File "C:\Programme\Python23\Scripts\win32_postinstall.py", line 86, in ? apachediroptions = getApacheDirOptions() File "C:\Programme\Python23\Scripts\win32_postinstall.py", line 45, in getApacheDirOptions apachekey = regkey(win32con.HKEY_LOCAL_MACHINE, "Software").childkey("Apache Group").childkey("Apache") File "C:\Programme\Python23\Scripts\win32_postinstall.py", line 34, in childkey return regkey(self.key, subkeyname) File "C:\Programme\Python23\Scripts\win32_postinstall.py", line 32, in __init__ self.key = win32api.RegOpenKey(parent, subkeyname) pywintypes.error: (2, 'RegOpenKeyEx', 'Das System kann die angegebene Datei nicht finden.') Exception exceptions.AttributeError: "regkey instance has no attribute 'key'" in <bound method regkey.__del__ of <__main__.regkey instance at 0x00CF1440>> ignored *** run_installscript: internal error 0xFFFFFFFF *** I checked the registry and found that the key mentioned in the error message does indeed not exist. Is this a failure in my apache configuration/installation or is the installation package of mod_python incorrect? Are there any experiences with the abovementioned configuration? Thanx in advance Peter

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invalid token problem ?
by tonino.greco＠gmail.com Sept. 2, 2004

Sept. 2, 2004

Hi, I have a xml field: <Cell Col="2" Row="10">="Actual Asset mix "&text($C$46,"dd-mmm-yyyy")</Cell> ^ | this is column 56 and am getting the following error: xml.sax._exceptions.SAXParseException: <stdin>:21:56: not well-formed (invalid token) I have used the : self.data += saxutils.escape(characters, self.transhash) and transhash has : transhash = { '"' : '"', '&' : '&' } Can anyone please explain why I am getting the error ? What am I missing ?? THANKS :)

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Re: about presicion
by mensanator＠aol.com Sept. 2, 2004

Sept. 2, 2004

Alex Martelli wrote: > mensanator(a)aol.com <mensanator(a)aol.com> wrote: > ... > > > > I just tried it and found out it's not compatible with gmpy. > > > > > > By "it" do you mean Decimal, or Python 2.4 alpha 2? > > > > By "it", I meant gmpy 1.0 and Python 2.4. Trying to import the > > module says it can't use the Python23.dll. > > _Any_ binary extension Python module compiled for Python 2.3 cannot even > load (on Windows) with Python 2.4 -- this has always been true on > Windows between any two releases of Python and will presumably continue > to be so for the foreseeable future. What I meant was the OP can't compare Decimal and gmpy unless he has a version of gmpy that runs in 2.4. Or has a version of Decimal that runs in 2.3. > > This doesn't mean that Python 2.4 "is not compatible with gmpy" or > viceversa: it just means you obviously need to use a gmpy binary (pyd > file) compiled for the version of Python you're using. Just as it would > be the case for any other binary extension module whatsoever. I didn't mean it wasn't compatible. I meant you can't use the 2.3 version of gmpy in the 2.4 alpha that's currently available, so I can't experiment with 2.4 because all my interesting programs are dependant on gmpy. Not everyone is a professional software developer, some of us ignorant users need to be told that. > > Unfortunately, compiling any binary extension module on Windows for > Python 2.4 requires Microsoft's very latest C++ compiler -- I do not own > a copy, nor do I have any PC normally running Windows XP, which is > required to run that compiler. Until Pyhon 2.3, I made do with a > Windows 98 session running under win4lin on one of my Linux machines, > and good old Microsoft Visual C++ 6 -- but such limited resources are > not sufficient any longer to compile Python binary extension modules for > Python 2.4. Since in terms of income-making (as well as leisure;-) I > work by now only on MacOSX, Linux, and OpenBSD machines, I am not going > to buy a PC loaded with Microsoft software just to be able to donate > precompiled Python binary extension modules to Windows users. How feasible is it that the end user could compile it himself? Would the command line c compiler from the MS SDK suffice or do you have to purchase the full .NET package? Would the source files need a lot of tweaking? > > > > > I think gmpy should > > > build happily with the latter, > > > > I'm using the pre-built Windows binary distribution. I wouldn't > > know how to re-build it. I assume that when Python 2.4 is final, > > I newer compatible version of gmpy will become available. > > Not by magic -- I hope somebody out there owns all the needed Microsoft > software and is interested in compiling gmpy for Windows under Python > 2.4 and making it available, but it won't be me. Unfortunately, us ignorant end users depend on the magic that is supplied by others. But that doesn't mean we're unwilling to help. I had no clue that there won't be any more Windows gmpy updates unless someone volunteers to help. I've got an XP machine and given a choice between abandoning Python completely and getting a copy of the MS compiler... Of course, I realize that handing someone a box of wrenches doesn't make them a mechanic. But we always have this newsgroup. I would rather try and fail than see gmpy whither away from lack of interest. > > > > > and interoperate sensibly with Decimal > > > anyway -- as gmpy's author I'd be quite happy to fix gmpy if it's > > broken > > > in either respect. > > > > Were you aware that there is apparently a memory leak in the > > gmpy.divm() function? Calling it several million time caused my > > computer to run out of virtual memeory. Luckily, I was able to > > work around it using the gmpy.invert() which didn't consume any > > memory regardless of how many times it was called. > > No, I was not aware of that -- I'll look into it, thanks. > > > Alex

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txt2xls
by michele.simionato＠gmail.com Sept. 2, 2004

Sept. 2, 2004

In would like to convert very simple text files into .xls files and I need some help. Here is the format of a typical file: # begin table.txt This should go in the first row, first column. This should go in the first row, second column. ==== This should go in the second row, first column. This should go in the second row, second column. ==== This should go in the third row, first column. This should go in the third row, second column. # end table.txt "====" separates different rows, whereas different colums are separated by an empty line. table.txt should be converted into a table.xls file containing a 3x2 table like this: ================================ ================================ This should go in the first row, This should go in the first row, first column. second column. -------------------------------- -------------------------------- This should go in the second row, This should go in the second row, first column. second column. -------------------------------- -------------------------------- This should go in the third row, This should go in the third row, first column. second column. ================================ ================================ I use OpenOffice on Linux, but I have no experience at all about the .xls format, so I would welcome help/pointers and especially snippets of code ;) TIA, Michele Simionato

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