🌐 Mailman 3 June 2010 - Python-list - python.org

Re: Python dynamic attribute creation
by WANG Cong June 30, 2010

June 30, 2010

On 06/29/10 17:48, Andre Alexander Bell <post(a)andre-bell.de> wrote: > On 06/25/2010 03:15 PM, WANG Cong wrote: >> 1) Modifying a class attribute is metaprogramming, and this is modifying >> a class, i.e. adding a new attribute to it, thus this should belong >> to metaprogramming. (I know, strictly speaking, maybe my definition of >> "metaprogramming" here is incorrect, I _do_ welcome someone could >> correct me if I am really wrong, but that is not the main point here, >> please don't go off-topic.) > > We should define meta programming a little more. First attempt: > > Programming is the art of writing down instructions such that when > executed accordingly will do what has been pre-specified. > > Meta programming is the art of writing down instructions such that when > executed accordingly will program instructions that when executed > accordingly will do what has been pre-specified. > >>From this definition I would argue that a dynamic attribute assignement > is _not_ meta programming. It is just modifying an object. > Yeah, probably this is the correct and strict definition of "metaprogramming". Thanks for correction. However, as I said above, I just wanted to borrow the word "metaprogramming" to express my meaning. What I meant is actually programming classes, you can call it "class-programming" if not "metaprogramm". <snip> >> 3) Thus, allowing dynamic attribute creation by assignment _by default_ >> is not a good design for me. It is not obvious at all to see if I am >> doing metaprogramming at a first glance. > > As said previously I don't think one should differentiate between meta > programming and programming within the language, since the former is > nothing different than the latter. > If you check other programming language rather than Python, it is different. Even in Ruby which is also a dynamic language. <snip> > Python is not pure OO as others already did explain. You may still use > it in pure OO style. > Yeah, even C can also have some OO style. But that is not the point. <snip> > >> 1) Disallow dynamic attribute creations by assignments _by default_, >> thus I expect an error when I do: > > So far I only did tell you _how_ it is in Python. If I understand your > question about the design of the language correctly than you would like > Python to detect the typo. Let's for the moment assume that the > declaration would be decoupled from assigning a value. > Nope, I would like Python not to allow adding a new attribute via an assignment by default, detecting the typo is a side-effect. > The first thing that would have to change is that in a class declaration > we would have to specify at least the names of the attributes and > methods. E.g. > > class Sample(object): > var a > def __init__(self): > self.a = 1 > > s = Sample() > s.b = 1 > -> Exception > > This however would furthermore change the way you would have to write a > function and a method due to possible internal variables > > def somefunc(): > var a > var b > a = 1 > b = 2 > return a+b > > As soon as you would need a variable you would always first have to > declare that variable and then assign a value. > > Even on the interactive shell you would have to do so: > >>>> var a >>>> a = 1 >>>> b = 2 > -> Exception > > Why would this declaration be necessary on the shell and in the > function/method? Declaring a variable means adding that variable to the > namespace, i.e. the underlying dictionary. There is one in each object, > the locals() of a function or even the __dict__ of a module. > > The downside of this is that Python has no such thing as a variable > without a value. Still you would need such a thing for this approach > >>>> var a >>>> a > -> should raise an variable 'unset' exception > > The underlying dictionary would need the ability to store keys (variable > names) without values. > > This approach increases the code length considerably, just to catch the > typos. > > Keep in mind that the module you are writing in is just an object as is > any function or method. So using local variables therein you are doing > exactly what you want to abandon from the OOP part. > Hmm, this looks really appealing. But if so why setattr() still exists? What is it for if we can do the same thing via assignments? Also, in order to be perfect, Python should accept to add dynamic attributes dynamically, something like PEP 363. That doesn't happen. Thanks! -- Live like a child, think like the god.

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pyc runtime error
by Baris CUHADAR June 30, 2010

June 30, 2010

Can anyone explain this unexpected behavior? all files chmod 755, i've compiled x.py with py_compilefiles, also tried within python console with "import x" system: centos 5.4 32bit This a PATH related problem i think? [root@centos-14 cgi-bin]# ./x.pyc : command not found ./x.pyc: line 2: syntax error near unexpected token `)' ./x.pyc: line 2: `��)Lc@sdGHdGHdkZeiGHdS(sContent-Type:text/ html' [root@centos-14 cgi-bin]# python x.pyc Content-Type:text/html python 2.4.3 (#1, Sep 3 2009, 15:37:12) [GCC 4.1.2 20080704 (Red Hat 4.1.2-46)] -------------------------------------------------------------------------------------------- x.py file content: #!/usr/bin/env python print "Content-Type:text/html\n\n" print "python" import sys print sys.version --------------------------------------------------------------------------------------------

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Re: [python] how to ensure item in list or dict bind with "an uuid meaning" integer type ID?
by Tim Roberts June 30, 2010

June 30, 2010

kee chen <keekychen.shared(a)gmail.com> wrote: > >I have 2 lists stored in 2 text files may have duplicated records, the raw >data looks like this: >lfruit lcountry >====== ========= >orange japan >pear china >orange china >apple american >cherry india >lemon china >lemon japan >strawberry korea >banana thailand > australia >basically, what I want is: > 1. all of the duplicated records need to be removed and > 2. the unique items need bind with an unique integer ID, something like a >PK in database, no sort needed. >but before you give answer here, pls also read below. You need a database. What you're talking about here is exactly the kind of thing that an SQL database can provide. Sqlite is simple and lightweight, and can do your unique checks and your join without even breaking a sweat. If you don't like that, there are pure Python SQL engines available that are even simpler. Why reinvent the whell? What you want already exists. -- Tim Roberts, timr(a)probo.com Providenza & Boekelheide, Inc.

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Python profiler usage with objects
by harit June 30, 2010

June 30, 2010

Hi, I have a specific question regarding the usage of profiler. I am new to python programming I am trying to profile a function which I want to invoke as a class method, something like this import profile class Class: def doSomething(): do here .. def callMethod(): **self.doSomething()** instead of this I want to use **profile.run(self.doSomething())** but the profile.run expects the string inside it and I get error TypeError: exec: arg 1 must be a string, file, or code object Can somebody please help? Thank you

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Re: Why Python3
by Carl Banks June 30, 2010

June 30, 2010

On Jun 27, 5:12 pm, Terry Reedy <tjre...(a)udel.edu> wrote: > I think that covers the main transitions in core Python. Nice post, but it's missing one thing. The main benefit of Python 3 for Joe Q. Scripter is this: The Python team doesn't have to spend any effort on maintaining a lot of old obsolete cruft, and can devote that time to fixing bugs and maintaining useful stuff instead. So they will benefit even if they don't actually use new features. Carl Banks

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Re: [OT] Re: Why Is Escaping Data Considered So Magical?
by Lawrence D'Oliveiro June 30, 2010

June 30, 2010

In message <mailman.2332.1277785175.32709.python-list(a)python.org>, Kushal Kumaran wrote: > On Tue, Jun 29, 2010 at 5:56 AM, Lawrence D'Oliveiro > <ldo(a)geek-central.gen.new_zealand> wrote: > >> Why does this work, then: >> >> ldo@theon:hack> cat test.c >> #include <stdio.h> >> >> int main(int argc, char ** argv) >> { >> char buf[512]; >> const int a = 2, b = 3; >> snprintf(&buf, sizeof buf, "%d + %d = %d\n", a, b, a + b); >> fprintf(stdout, buf); >> return >> 0; >> } /*main*/ >> ldo@theon:hack> ./test >> 2 + 3 = 5 > > By accident. I have yet to find an architecture or C compiler where it DOESN’T work. Feel free to try and prove me wrong.

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The Icelandic Sheepdog,
by Camelot Entertainment June 30, 2010

June 30, 2010

The Icelandic Sheepdog, http://noizeystatic.blogspot.com/2070/06/icelandic-sheepdog-noizey-static-f… inherently comes from the spitz type, the dogs that landed on iceland by the Vikings.

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Re: Why are String Formatted Queries Considered So Magical?
by Carl Banks June 30, 2010

June 30, 2010

On Jun 28, 3:07 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote: > On Sun, 27 Jun 2010 21:02:57 -0700, Stephen Hansen > <me+list/pyt...(a)ixokai.io> declaimed the following in > gmane.comp.python.general: > > > (This is an area where parametrized queries is even more important: but > > I'm not sure if MySQL does proper prepared queries and caching of > > execution plans). > > MySQL version 5 finally added prepared statements and a discrete > parameter passing mechanism... > > However, since there likely are many MySQL v4.x installations out > there, which only work with complete string SQL, MySQLdb still formats > full SQL statements (and it uses the Python % string interpolation to do > that, after converting/escaping parameters -- which is why %s is the > only allowed placeholder; even a numeric parameter has been converted to > a quoted string before being inserted in the SQL). > > It would be nice if MySQLdb could become version aware in a future > release, and use prepared statements on v5 engines... I doubt it can > drop the existing string based queries any time soon... Consider the > arguments about how long Python 2.x will be in use (I'm still on 2.5)... > Imagine the sluggishness in having database engines converted > (especially in a shared provider environment, where the language > specific adapters also need updating -- ODBC drivers, etc.) Thanks, your replies to this subthread have been most enlightening. Carl Banks

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[ANN] git JSONRPC web service and matching pyjamas front-end
by Luke Kenneth Casson Leighton June 29, 2010

June 29, 2010

as more than just a proof-of-concept but to get pyjamas out of looking like "a nice toy, doesn't do much, great demos, shame about real life", i've created yet another git repository browser. this one, thanks to pyjamas, obviously runs as both a desktop application and also as a web application - same source code. pyjamasgitweb is actually two independent happily small projects. the first is simply a JSONRPC-based git web server (in python, using python-git) and the second is a matching front-end. the front-end is happily bare but functional. a demo is here (please be nice to it) where you will see immediately a total lack of colour or even borders: http://pyjs.org/pygit if anyone wants the source code, or to help contribute, it's at: git clone gitolite@pyjs.org:pyjamasgitweb to start the server, read the README, install the dependencies, then do: $ cd jsonservice $ python srv.py {path to top level of repository} & $ cd ../pyjamas $ ./build.sh # requires symlink ~/bin/pyjsbuild to sandbox $ firefox http://127.0.0.1:8000/outputJSONRPCService.html & $ python JSONRPCService.py # for the desktop version l.

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Re: I strongly dislike Python 3
by falk＠green.rahul.net June 29, 2010

June 29, 2010

In article <mailman.2309.1277758252.32709.python-list(a)python.org>, Stephen Hansen <me+list/python(a)ixokai.io> wrote: >> >> Uhmm, just add the parenthesis to your old scripts. You can >> do that without breaking on 2.x. > >Only sort of. But in Python 2.6+, you only need to "from __future__ >import print_function" to make code work in both 2.x and 3.x (at least >insofar as the print situation is concerned). Nice. Once 100% of the installed base is at 2.6, I'll finally be able to write code that compatible with 3.0. -- -Ed Falk, falk(a)despams.r.us.com http://thespamdiaries.blogspot.com/

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