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  • Should I use a class in this: Reading a XML file using lxml.

    - by PulpFiction
    Hi everyone. This question is in continuation to my previous question, in which I asked about passing around an ElementTree. I need to read the XML files only and to solve this, I decided to create a global ElementTree and then parse it wherever required. My question is: Is this an acceptable practice? I heard global variables are bad. If I don't make it global, I was suggested to make a class. But do I really need to create a class? What benefits would I have from that approach. Note that I would be handling only one ElementTree instance per run, the operations are read-only. If I don't use a class, how and where do I declare that ElementTree so that it available globally? (Note that I would be importing this module) Please answer this question in the respect that I am a beginner to development, and at this stage I can't figure out whether to use a class or just go with the functional style programming approach.

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  • What do I do with a Concrete Syntax Tree?

    - by Cap
    I'm using pyPEG to create a parse tree for a simple grammar. The tree is represented using lists and tuples. Here's an example: [('command', [('directives', [('directive', [('name', 'retrieve')]), ('directive', [('name', 'commit')])]), ('filename', [('name', 'f30502')])])] My question is what do I do with it at this point? I know a lot depends on what I am trying to do, but I haven't been able to find much about consuming/using parse trees, only creating them. Does anyone have any pointers to references I might use? Thanks for your help.

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  • nested list comprehension using intermediate result

    - by KentH
    I am trying to grok the output of a function which doesn't have the courtesy of setting a result code. I can tell it failed by the "error:" string which is mixed into the stderr stream, often in the middle of a different conversion status message. I have the following list comprehension which works, but scans for the "error:" string twice. Since it is only rescanning the actual error lines, it works fine, but it annoys me I can't figure out how to use a single scan. Here's the working code: errors = [e[e.find('error:'):] for e in err.splitlines() if 'error:' in e] The obvious (and wrong) way to simplify is to save the "find" result errors = [e[i:] for i in e.find('error:') if i != -1 for e in err.splitlines()] However, I get "UnboundLocalError: local variable 'e' referenced before assignment". Blindly reversing the 'for's in the comprehension also fails. How is this done? THanks. Kent

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  • Can UML be used to model a Functional program?

    - by iestyn
    More specifically, how do you model a functional program, or one developed using the Functional Style (without classes) using a diagram, and not textual representation, is it at all possible and could someone please direct me towards the nearest application that would do this (open source, of free as in beer, if you please)

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  • A Tkinter StringVar() Question

    - by Graham
    I would like to create a StringVar() that looks something like this: someText = "The Spanish Inquisition" #Here's a normal variable whose value I will change eventually TkEquivalent = StringVar() #and here's the StringVar() TkEquivalent.set(string(someText)) #and here I set it equal to the normal variable. When someText changes, this variable will too... HOWEVER: TkEquivalent.set("Nobody Expects " + string(someText)) If I do this, the StringVar() will no longer automatically update! How can I include that static text and still have the StringVar() update to reflect changes made to someText? Thanks for your help.

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  • Django store regular expression in DB which then gets evaluated on page

    - by John
    Hi, I want to store a number of url patterns in my django model which a user can provide parameters to which will create a url. For example I might store these 3 urls in my db where %s is the variable parameter provided by the user: www.thisissomewebsite.com?param=%s www.anotherurl/%s/ www.lastexample.co.uk?param1=%s&fixedparam=2 As you can see from these examples the parameter can appear anywhere in the string and not in a fixed position. I have 2 models, one holds the urls and one holds the variables: class URLPatterns(models.Model): pattern = models.CharField(max_length=255) class URLVariables(models.Model): pattern = models.ForeignKey(URLPatterns) param = models.CharField(max_length=255) What would be the best way to generate these urls by replacing the %s with the variable in the database. would it just be a simple replace on the string e.g: urlvariable = URLVariable.objects.get(pk=1) pattern = url.pattern url = pattern.replace("%s", urlvariable.param) or is there a better way? Thanks

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  • wav file manupalation

    - by kaushik
    I want get the details of the wave such as its frames into a array of integers. Using fname.getframes we can ge the properties of the frame and save in list or anything for writing into another wav or anything,but fname.getframes gives information not in integers some thing like a "/xt/x4/0w' etc.. But i want them in integer so that would be helpful for manupation and smoothening join of 2 wav files

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  • KindError: Property r must be an instance of SecondModel, why ?

    - by zjm1126
    class FirstModel(db.Model): p = db.StringProperty() r=db.ReferenceProperty(SecondModel) class SecondModel(db.Model): r = db.ReferenceProperty(FirstModel) class sss(webapp.RequestHandler): def get(self): a=FirstModel() a.p='sss' a.put() b=SecondModel() b.r=a b.put() a.r=b a.put() self.response.out.write(str(b.r.p)) the error is : Traceback (most recent call last): File "D:\Program Files\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 511, in __call__ handler.get(*groups) File "D:\zjm_code\helloworld\a.py", line 158, in get a.r=b File "D:\Program Files\Google\google_appengine\google\appengine\ext\db\__init__.py", line 3009, in __set__ value = self.validate(value) File "D:\Program Files\Google\google_appengine\google\appengine\ext\db\__init__.py", line 3048, in validate (self.name, self.reference_class.kind())) KindError: Property r must be an instance of SecondModel thanks

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  • Rewriting Live TCP/IP (Layer 4) Streams

    - by user213060
    I want to rewrite TCP/IP streams. Ettercap's etterfilter command lets you perform simple live replacements of TCP/IP data based on fixed strings or regexes. Example: if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "gzip")) { replace("gzip", " "); msg("whited out gzip\n"); } } if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "deflate")) { replace("deflate", " "); msg("whited out deflate\n"); } } http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? The rewriting should occur at the transport layer (Layer 4) as it does in this example, instead of a lower layer packet-based approach. Thanks!

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  • How do you extend the Site model in django?

    - by John Giotta
    What is the best approach to extending the Site model in django? Creating a new model and ForeignKey the Site or there another approach that allows me to subclass the Site model? I prefer subclassing, because relationally I'm more comfortable, but I'm concerned for the impact it will have with the built-in Admin.

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  • Could random.randint(1,10) ever return 11?

    - by Tim Pietzcker
    When researching for this question and reading the sourcecode in random.py, I started wondering whether randrange and randint really behave as "advertised". I am very much inclined to believe so, but the way I read it, randrange is essentially implemented as start + int(random.random()*(stop-start)) (assuming integer values for start and stop), so randrange(1, 10) should return a random number between 1 and 9. randint(start, stop) is calling randrange(start, stop+1), thereby returning a number between 1 and 10. My question is now: If random() were ever to return 1.0, then randint(1,10) would return 11, wouldn't it?

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  • Convert sets to frozensets as values of a dictionary

    - by Space_C0wb0y
    I have dictionary that is built as part of the initialization of my object. I know that it will not change during the lifetime of the object. The dictionary maps keys to sets. I want to convert all the values from sets to frozensets, to make sure they do not get changed. Currently I do that like this: for key in self.my_dict.iterkeys(): self.my_dict[key] = frozenset(self.my_dict[key]) Is there a simpler way to achieve this? I cannot build frozenset right away, because I do not how much items will be in each set until i have built the complete dictionary.

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  • Replacing text with variables

    - by Steve
    I have to send out letters to certain clients and I have a standard letter that I need to use. I want to replace some of the text inside the body of the message with variables. Here is my maturity_letter models.py class MaturityLetter(models.Model): default = models.BooleanField(default=False, blank=True) body = models.TextField(blank=True) footer = models.TextField(blank=True) Now the body has a value of this: Dear [primary-firstname], AN IMPORTANT REMINDER… You have a [product] that is maturing on [maturity_date] with [financial institution]. etc Now I would like to replace everything in brackets with my template variables. This is what I have in my views.py so far: context = {} if request.POST: start_form = MaturityLetterSetupForm(request.POST) if start_form.is_valid(): agent = request.session['agent'] start_date = start_form.cleaned_data['start_date'] end_date = start_form.cleaned_data['end_date'] investments = Investment.objects.all().filter(maturity_date__range=(start_date, end_date), plan__profile__agent=agent).order_by('maturity_date') inv_form = MaturityLetterInvestments(investments, request.POST) if inv_form.is_valid(): sel_inv = inv_form.cleaned_data['investments'] context['sel_inv'] = sel_inv maturity_letter = MaturityLetter.objects.get(id=1) context['mat_letter'] = maturity_letter context['inv_form'] = inv_form context['agent'] = agent context['show_report'] = True Now if I loop through the sel_inv I get access to sel_inv.maturity_date, etc but I am lost in how to replace the text. On my template, all I have so far is: {% if show_letter %} {{ mat_letter.body }} <br/> {{ mat_letter.footer }} {% endif %} Much appreciated.

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  • Fastest method in merging of the two: dicts vs lists

    - by tipu
    I'm doing some indexing and memory is sufficient but CPU isn't. So I have one huge dictionary and then a smaller dictionary I'm merging into the bigger one: big_dict = {"the" : {"1" : 1, "2" : 1, "3" : 1, "4" : 1, "5" : 1}} smaller_dict = {"the" : {"6" : 1, "7" : 1}} #after merging resulting_dict = {"the" : {"1" : 1, "2" : 1, "3" : 1, "4" : 1, "5" : 1, "6" : 1, "7" : 1}} My question is for the values in both dicts, should I use a dict (as displayed above) or list (as displayed below) when my priority is to use as much memory as possible to gain the most out of my CPU? For clarification, using a list would look like: big_dict = {"the" : [1, 2, 3, 4, 5]} smaller_dict = {"the" : [6,7]} #after merging resulting_dict = {"the" : [1, 2, 3, 4, 5, 6, 7]} Side note: The reason I'm using a dict nested into a dict rather than a set nested in a dict is because JSON won't let me do json.dumps because a set isn't key/value pairs, it's (as far as the JSON library is concerned) {"a", "series", "of", "keys"} Also, after choosing between using dict to a list, how would I go about implementing the most efficient, in terms of CPU, method of merging them? I appreciate the help.

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  • how to render custom columns with a GenericTreeModel

    - by Giorgio Gelardi
    I have to display some data in a treeview. The "real" data model is huge and I cannot copy all the stuff in a TreeStore, so I guess I should use a GenericTreeModel to act like a virtual treeview. Btw the first column is the classic icon+text style and I think I should declare a column with a CellRendererPixbuf (faq sample), but I'm not sure what the model methods on_get_n_columns() and on_get_value() should return. It's both a Pixbuf and a string value for the same column. Any help will be appreciated.

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  • any faster alternative??

    - by kaushik
    have file data of format 3.343445 1 3.54564 1 4.345535 1 2.453454 1 and so on upto 1000 lines and i have number given such as a=2.44443 for the given file i need to find the row number of the numbers in file which is most close to the given number "a" how can i do this i am presently doing by loading whole file into list and comparing each element and finding the closest one any other better faster method?

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  • How do I set prifix to django contrib tables names?

    - by Software Enthusiastic
    HI One of my requirement is to have prefix on all the tables of the django based project (Because db is hosted on shared server). I have used db_table Meta option to set the prefix for the tables which I have created. Now my query is how do I set the prefix for tables provided by django.contrib. Instead of auth_group django should create prefix_auth_group.... How do I do that? Thank you very much...

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  • Read data from specific memory address

    - by rapid
    Hello. How can I read (and put into new variable) data stored at specific memory address? For instance I know that: <nfqueue.queue; proxy of <Swig Object of type 'queue *' at 0xabd2b00> > And I want to have data stored at 0xabd2b00 in new variable so that I can work and use all functionalities of the object. Let's assume that I don't have access to the original variable that created this object.

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  • PyQt4.QtCore doesn't contain many of its classes and attributes

    - by toc777
    Hi everyone, I have built PyQt4 from source and everything went smoothly until I tried to use some of the classes and attributes located in QtCore. For some reason QtCore is missing a lot of functionality and data that should be there. For example from PyQt4.QtCore import QT_VERSION_STR is an import error. There were no errors or warnings given when building the packages and I have also tried with the PyQt packages from yum but I have the same problem. Has anyone else encountered this problem before? Thanks.

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  • Efficient job progress update in web application

    - by Endru6
    Hi, Creating a web application (Django in my case, but I think the question is more general) that is administrating a cluster of workers doing queued jobs, there is a need to track each jobs progress. When I've done it using database UPDATE (PostgreSQL in this case), it severely hits the database performance, because each UPDATE creates a new row in a table, and in my case only vacuuming DB removes obsolete rows. Having 30 jobs running and reporting progress every 1 minute DB may require vacuuming (and it means huge slow downs on a front end side for all the employees working with the system) every 10 days. Because the progress information isn't critical, ie. it doesn't have to be persistent, how would you do the progress updates from jobs without using an overhead database implies? There are 30 worker servers, each doing 1 or 2 jobs simultaneously, 1 front end server which serves a web application to users, and 1 database server.

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  • Using SQLAlchemy, how can I return a count with multiple columns

    - by Andy
    I am attempting to run a query like this: SELECT comment_type_id, name, count(comment_type_id) FROM comments, commenttypes WHERE comment_type_id=commenttypes.id GROUP BY comment_type_id Without the join between comments and commenttypes for the name column, I can do this using: session.query(Comment.comment_type_id,func.count(Comment.comment_type_id)).group_by(Comment.comment_type_id).all() However, if I try to do something like this, I get incorrect results: session.query(Comment.comment_type_id, Comment.comment_type, func.count(Comment.comment_type_id)).group_by(Comment.comment_type_id).all() I have two problems with the results: (1, False, 82920) (2, False, 588) (3, False, 4278) (4, False, 104370) Problems: The False is not correct The counts are wrong My expected results are: (1, 'Comment Type 1', 13820) (2, 'Comment Type 2', 98) (3, 'Comment Type 2', 713) (4, 'Comment Type 2', 17395) How can I adjust my command to pull the correct name value and the correct count?

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