🌐 Mailman 3 June 2009 - Python-list - python.org

Unexpected behaviour of inner functions/ decorators
by Francesco Bochicchio June 30, 2009

June 30, 2009

Hi all, I found a strange (for me) behaviour of inner function. If I execute the following code: # file in_f.py ----------- def dec_f(f): def inner_f(): if f.enabled: f() return inner_f @dec_f def funct(): print "Ciao" funct.enabled = True funct() # end of file ----------------- I get the following exception: File "/Users/fb/Documents/Prove python/in_f.py", line 15, in <module> funct() File "/Users/fb/Documents/Prove python/in_f.py", line 5, in inner_f if f.enabled: AttributeError: 'function' object has no attribute 'enabled' The same happens when I rebind explicitely the function name instead of using the decorator: def funct(): print "Ciao" funct = dec_f(funct) It looks like the decorator uses an older instance of 'funct', which does not yet have the attribute dinamically attached to it. This seem to be confirmed by the fact that adding the attribute before rebinding the function name, the problem disappear: def funct(): print "Ciao" funct.enabled = False # this fixes the problem funct = dec_f(funct) So I have a workaround, but still don't understant why the original code does not work. Anyone can point me to an explanation? Thanks in advance Ciao ------- FB

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Python Imaging Library download link broken?
by peter June 30, 2009

June 30, 2009

Just got a new computer and I'm trying to download my favourite applications. All's well until I get to PIL, and here pythonware and effbot both return a 502 Proxy error. Is this just a temporary glitch, or something more serious? And if it's the latter, is there any alternative source? Peter

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Timeout when connecting to sybase DBS
by eranlevi June 30, 2009

June 30, 2009

Hi All, I'm using the Sybase module for connecting and using a sybase DBS. When I try to connect when the DBS is down, it take approximately 4 minutes for the function (conn.ct_connect) to return with an error. I have looked for a timeout parameter to limit the 4 minutes to something more reasonable but couldn't find one. Can anyone please help? BTW, I'm using Sybase.connect(<DBS name>, <Username>, <Password>, datetime='auto') Thanks Gil

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Re: Drawing in PDF
by Grant Edwards June 30, 2009

June 30, 2009

On 2009-06-30, Eduardo Lenz <lenz(a)joinville.udesc.br> wrote: > Em Seg 29 Jun 2009, às 20:39:22, Lawrence D'Oliveiro escreveu: >> In message <b4daf01a-50e9-4038-9db0- >> >> d7fe56d0593f(a)g19g2000yql.googlegroups.com>, Jun wrote: >> > ... is there open source solution ? >> >> Poppler? > > pypdf -- http://pybrary.net/pyPdf/ > > > A Pure-Python library built as a PDF toolkit. It is capable of: > > * extracting document information (title, author, ...), > * splitting documents page by page, > * merging documents page by page, > * cropping pages, > * merging multiple pages into a single page, > * encrypting and decrypting PDF files. While it may be a pure-python library, the problem is that AFAICT it doesn't actually solve the problem at hand. The requirement is to "draw" on the pages of an existing PDF document (add annotations). > By being Pure-Python, it should run on any Python platform > without any dependencies on external libraries. It can also > work entirely on StringIO objects rather than file streams, > allowing for PDF manipulation in memory. It is therefore a > useful tool for websites that manage or manipulate PDFs. True, but does it allow you to add text/lines/etc. to a page? -- Grant

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Re: using input(), raw_input() to allow user to run different functions
by rhvonlehe＠gmail.com June 30, 2009

June 30, 2009

On Jun 29, 5:22 pm, MRAB <pyt...(a)mrabarnett.plus.com> wrote: > rhvonl...(a)gmail.com wrote: > > Something's been giving me difficulty.. > > > We have a USB-attached device that we frequently debug with simple > > python scripts. The model has always been that each script logs on to > > the device, does something, then logs off. As it turns out, we have > > mostly written scripts as unit tests for each API command. So, we'll > > call one script that will configure a process on the device, and a > > separate script that will retrieve the results of that process. > > > The model is changing inside the device such that all settings will be > > lost when we log off. This means we'll have to merge a bunch of > > scripts in various ways. > > > I thought it would be neat if I could have one master python script do > > the logon, then allow the user to input the name of a previously- > > written script he wanted to execute while logged on. Finally, when > > exiting the master script, the user would logout from the device. > > > I'm trying to test this by using input() or raw_input() to get the > > function the user wants to execute. I'm not having much luck. Here's > > an example: > > > Shell.py: > > #! /usr/bin/env python > > from CollectNDResults import * > > ... > > request = input('Script shell >>> ') > > print request > > exec (request) ## I realize the parentheses are not needed > > ... > > > When I run Shell.py I get this: > > > Script shell >>> CollectNDResults > > <function CollectNDResults at 0x00AA75F0> > > Traceback (most recent call last): > > File "./Shell.py", line 35, in ? > > Shell(sys.argv[1:]) > > File "./Shell.py", line 24, in Shell > > exec (request) > > TypeError: exec: arg 1 must be a string, file, or code object > > > Is there a good reference for me to figure out how to turn my function > > name into the code object that I want to execute? Is there a better > > way to do what I'm trying to do? > > >>> def foo(): > print "running foo" > > >>> import sys > >>> func_name = "foo" > >>> getattr(sys.modules[__name__], func_name)() > running foo Excellent replies, both. I'll get a lot of mileage out of this, thanks!

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Re: Drawing in PDF
by Jun June 30, 2009

June 30, 2009

On Jun 30, 12:09 am, Emile van Sebille <em...(a)fenx.com> wrote: > On 6/29/2009 2:51 PM Jun said... > > > HEllo, > > > I've a pdf file, and i want to draw some additional stuff on it, by > > example : some markup .... notation. Anyone has idea how to do that ? > > thank you in advance. > > ISTM that reportlab's commercial offering does that. > > http://www.reportlab.com/sectors/developers/ > > Emile Thanks a lot, is there open source solution ?

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Re: identify checksum type?
by Scott David Daniels June 30, 2009

June 30, 2009

Christian Heimes wrote: > PK schrieb: >> Given a checksum value, whats the best way to find out what type it is? >> >> meaning. I can use hashlib module and compute a md5 or sha1 for a given data >> etc..but given a checksum value say "d2bda52ee39249acc55a75a0f3566105" whats >> the best way for me to identify if its a sha1 or md5 or anyother sum type >> for that matter? >> >> is there a nice way to do this in python? > > As far as I know there is no way to identify a checksum by its value. A > checksum is just a number. You can try an educated guess based on the > length of the checksum. Or you can try all hash algorithms until you get > a hit but that may lead to security issues. > > Some applications prefix the hash value with an identifier like "{MD5}" > or "{SHA1}". > > Christian > fortunately, the hashlib checksums can be distinguished by their length On the newly minted 3.1: import hashlib text = b'BDFL forever; FLUFL for frequently' for name in 'md5 sha1 sha224 sha256 sha384 sha512'.split(): result = getattr(hashlib, name)(text).hexdigest() print('%6s:%3d %s' % (name, len(result), result)) md5: 32 457484d2817fbe475ab582bff2014e82 sha1: 40 242076dffbd432062b439335438f08ba53387897 sha224: 56 89c0439b1cf3ec7489364a4b8e50b3ba196706eecdb5e5aec6d6290f sha256: 64 e10938435e4b5b54c9276c05d5f5d7c4401997fbd7f27f4d4...807d sha384: 96 3fe7c7bf3e83d70dba7d59c3b79f619cf821a798040be2177...edb7 sha512:128 fe50d9f0c5780edb8a8a41e317a6936ec6305d856c78ccb8e...1fa0 You'll have to guess for adler32 vs. crc32 vs. seeded crc32, ... --Scott David Daniels Scott.Daniels(a)Acm.Org

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Re: Learning to use decorators with classes
by sk8in_zombi＠yahoo.com.au June 30, 2009

June 30, 2009

--- On Tue, 30/6/09, Bruno Desthuilliers <bruno.42.desthuilliers(a)websiteburo.invalid> wrote: > <ot> > Don't use '__name__', they are reserved for the > implementation. And FWIW, don't use '__name' unless you have > a really compelling reason to do so. > </ot> That was an honest mistake!. Noted :) > > > def search(self, **kw): > > print > 'Searching' > > ... > > > This can't work, and it's a FAQ FWIW - but since there's no > official c.l.py FAQ, we won't hold it against you !-) > Can you please point me to the FAQ related to this snippet. I would be grateful. > def and class are both *executable* statements (yes, > classes and functions creation - like almost anything in > Python - are run-time operations). > > The first one creates a function object - *wherever* it > happens - and bind the function object to the function's > name in the current namespace. Think of it as an equivalent > of the following javascript snippet: > > var func_name = function(arg) { /* > function's body */ }; > > The second statement - class - builds a class object from > the names defined in the class statement's body (that is, > names defined in the class statement's body will become > attributes of the class object). > > Now about the 'methods' and 'self' stuff... > > First understand that there's *nothing* magical with > 'self'. It's *not* a keyword. It's only a naming convention, > and you could use any legal Python identified instead. > > The reason we have to explicitly mention it as first > argument of the function is that it's the only way the > function's body can get access to the current instance. What > happens is (overly simplified) that during attribute > resolution, when the found attribute happens to be a > function, this function is wrapped - together with the > instance on which the attribute was looked up and it's class > - into a callable method object. Then when you call > this method object, it inserts the instance as first > argument to the function call, and returns the result of the > function call (if you want to read more about this and how > computed attributes are implemented in Python, google for > 'descriptor protocol'). > > IOW, and to make a long story short, calling > instance.method is the same as calling > Class.method(instance). > > Thank you very much for your explanation. I will remember these points by heart. > Ok, now to the point: when you call getConnection within > the class statement's body, there's no magical "self" > keyword poiting to an instance, and since the class itself > doesn't yet exists, so there's *no* way you could get at an > instance of it anyway !-) > > There are many ways to solve your problem, the simplest > bing probably to write another decorator calling on the > first one, ie: > > > def connected_method(func): > def connected(self, *args, **kw): > wrapped = > getConnection(self.__this, self.__that)(func) > return wrapped(*args, **kw) > > return connected > > > Note that this may not be that efficient - you'll have > quite a few function calls involved here. > I was trying follow the concept of decorators with arguments and I can now understand why it failed, thanks. Thanks and regards, SZ Access Yahoo!7 Mail on your mobile. Anytime. Anywhere. Show me how: http://au.mobile.yahoo.com/mail

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Re: Passing parameters for a C program in Linux.
by venutaurus539＠gmail.com June 30, 2009

June 30, 2009

On Jun 30, 5:42 pm, Petr Messner <petr.mess...(a)gmail.com> wrote: > Hi, > > this can be done using module "subprocess"; there is also function > popen() in module "os" and module popen2, but they are deprecated > since Python 2.6. > > PM > > 2009/6/30 venutaurus...(a)gmail.com <venutaurus...(a)gmail.com>: > > > Hi all, > > I have to write an automted script which will test my c > > program. That program when run will ask for the commands. For example: > > > local-host# ./cli > > Enter 1 for add > > Enter 2 for sub > > Enter 3 for mul > > 1 -------Our option > > Enter two numbers > > 44 33 -------- Our option > > Result is 77 > > > As shown in the above example it lists all the options and waits for > > user input and once given, it does some operations and waits for some > > more. This has to be automated. > > > Can someone give suggestions how to do this in Python (Linux Platform > > in particular). > > > Thank you, > > Venu. > > -- > >http://mail.python.org/mailman/listinfo/python-list > > Can you give some more explanation about how exactly this can be done.. Thanks for reply, Venu

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ImageEnhance.Contrast - is this fishy or what?
by roop June 30, 2009

June 30, 2009

I was browsing ImageEnhace.py, and found something that I thought was odd in class Contrast: class Contrast(_Enhance): "Adjust image contrast" def __init__(self, image): self.image = image mean = reduce(lambda a,b: a+b, image.convert("L").histogram())/ 256.0 self.degenerate = Image.new("L", image.size, mean).convert (image.mode) Isn't reduce(lambda a,b: a+b, image.convert("L").histogram()) the same as (image.size[0] * image.size[1]) - just count the number of pixels in the image? (Afaik, the histogram is a list of 256 elements where the ith element gives the number of pixels with i as the pixel value (0 <= i < 256)). Is this actually fishy or have I got it all muddled up? Thanks, roop

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