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  • Iterating over a database column in Django

    - by curious
    I would like to iterate a calculation over a column of values in a MySQL database. I wondered if Django had any built-in functionality for doing this. Previously, I have just used the following to store each column as a list of tuples with the name table_column: import MySQLdb import sys try: conn = MySQLdb.connect (host = "localhost", user = "user", passwd="passwd", db="db") except MySQLdb.Error, e: print "Error %d: %s" % (e.args[0], e.args[1]) sys.exit (1) cursor = conn.cursor() for table in ['foo', 'bar']: for column in ['foobar1', 'foobar2']: cursor.execute('select %s from %s' % (column, table)) exec "%s_%s = cursor.fetchall()" % (table, column) cursor.close() conn.commit() conn.close() Is there any functionality built into Django to more conveniently iterate through the values of a column in a database table? I'm dealing with millions of rows so speed of execution is important.

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  • How to calculate cointegrations of two lists?

    - by Damiano
    Hello everybody! Thank you in advance for your help! I have two lists with some stocks prices, example: a = [10.23, 11.65, 12.36, 12.96] b = [5.23, 6.10, 8.3, 4.98] I can calculate the correlation of these two lists, with: import scipy.stats scipy.stats.pearsonr(a, b)[0] But, I didn't found a method to calculate the co-integration of two lists. Could you give me some advices? Thank you very much!

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  • Looking for: nosql (redis/mongodb) based event logging for Django

    - by Parand
    I'm looking for a flexible event logging platform to store both pre-defined (username, ip address) and non-pre-defined (can be generated as needed by any piece of code) events for Django. I'm currently doing some of this with log files, but it ends up requiring various analysis scripts and ends up in a DB anyway, so I'm considering throwing it immediately into a nosql store such as MongoDB or Redis. The idea is to be easily able to query, for example, which ip address the user most commonly comes from, whether the user has ever performed some action, lookup the outcome for a specific event, etc. Is there something that already does this? If not, I'm thinking of this: The "event" is a dictionary attached to the request object. Middleware fills in various pieces (username, ip, sql timing), code fills in the rest as needed. After the request is served a post-request hook drops the event into mongodb/redis, normalizing various fields (eg. incrementing the username:ip address counter) and dropping the rest in as is. Words of wisdom / pointers to code that does some/all of this would be appreciated.

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  • redirection follow by post

    - by lucas
    hi, just wonder how those air ticket booking website redirect the user to the airline booking website and then fill up(i suppose doing POST) the required information so that the users will land on the booking page with origin/destination/date selected? Is the technique used is to open up new browser window and do a ajax POST from there? Thanks.

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  • One-line expression to map dictionary to another

    - by No Such IP
    I have dictionary like d = {'user_id':1, 'user':'user1', 'group_id':3, 'group_name':'ordinary users'} and "mapping" dictionary like: m = {'user_id':'uid', 'group_id':'gid', 'group_name':'group'} All i want to "replace" keys in first dictionary with keys from second (e.g. replace 'user_id' with 'uid', etc.) I know that keys are immutable and i know how to do it with 'if/else' statement. But maybe there is way to do it in one line expression?

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  • Django ForeignKey _set on an inherited model

    - by neolaser
    I have two models Category and Entry. There is another model ExtEntry that inherits from Entry class Category(models.Model): title = models.CharField('title', max_length=255) description = models.TextField('description', blank=True) ... class Entry(models.Model): title = models.CharField('title', max_length=255) categories = models.ManyToManyField(Category) ... class ExtEntry(Entry): groups= models.CharField('title', max_length=255) value= models.CharField('title', max_length=255) ... I am able to use the Category.entry_set but I want to be able to do Category.blogentry_set but it is not available. If this is not available,then I need another method to get all ExtEntryrelated to one particular Category Thanks

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  • Choosing randomly all the elements in the the list just once

    - by Dalek
    How is it possible to randomly choose a number from a list with n elements, n time without picking the same element of the list twice. I wrote a code to choose the sequence number of the elements in the list but it is slow: >>>redshift=np.array([0.92,0.17,0.51,1.33,....,0.41,0.82]) >>>redshift.shape (1225,) exclude=[] k=0 ng=1225 while (k < ng): flag1=0 sq=random.randint(0, ng) while (flag1<1): if sq in exclude: flag1=1 sq=random.randint(0, ng) else: print sq exclude.append(sq) flag1=0 z=redshift[sq] k+=1 It doesn't choose all the sequence number of elements in the list.

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  • Is it possible in SQLAlchemy to filter by a database function or stored procedure?

    - by Rico Suave
    We're using SQLalchemy in a project with a legacy database. The database has functions/stored procedures. In the past we used raw SQL and we could use these functions as filters in our queries. I would like to do the same for SQLAlchemy queries if possible. I have read about the @hybrid_property, but some of these functions need one or more parameters, for example; I have a User model that has a JOIN to a bunch of historical records. These historical records for this user, have a date and a debit and credit field, so we can look up the balance of a user at a specific point in time, by doing a SUM(credit) - SUM(debit) up until the given date. We have a database function for that called dbo.Balance(user_id, date_time). I can use this to check the balance of a user at a given point in time. I would like to use this as a criterium in a query, to select only users that have a negative balance at a specific date/time. selection = users.filter(coalesce(Users.status, 0) == 1, coalesce(Users.no_reminders, 0) == 0, dbo.pplBalance(Users.user_id, datetime.datetime.now()) < -0.01).all() This is of course a non-working example, just for you to get the gist of what I'd like to do. The solution looks to be to use hybrd properties, but as I mentioned above, these only work without parameters (as they are properties, not methods). Any suggestions on how to implement something like this (if it's even possible) are welcome. Thanks,

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  • There is a system alert of (13, 'Permission denied'), how to solve that?

    - by Semanty
    def upload_file(request, step_id): def handle_uploaded_file (file): current_step = Step.objects.get(pk=step_id) current_project = Project.objects.get(pk=current_step.project.pk) path = "%s/upload/file/%s/%s" % (settings.MEDIA_ROOT, current_project.project_no, current_step.name) if not os.path.exists (path): os.makedirs(path) fd = open(path) for chunk in file.chunks(): fd.write(chunk) fd.close() if request.method == 'POST': form = UploadFileForm(request.POST, request.FILES) if form.is_valid(): handle_uploaded_file(request.FILES['file']) return HttpResponseRedirect('/success/url/') else: form = UploadFileForm() return render_to_response('projects/upload_file.html', { 'step_id': step_id, 'form': form, })

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  • add gtk.widget in a gnome Applet

    - by dominos
    Hi, I have a question : I write a little gnome applet, and when we click on a button i want to add a gtk.widget under the "gnome-panel" like the calendar of the clock-applet. But I don't know how to do this. It's my code : listButton = gtk.Button(_("lastest")) self.listTwitt = gtk.TreeView() mainLayout = gtk.VBox() mainLayout.pack_start(listButton) mainLayout.pack_start(self.listTwitt) self.applet.add(mainLayout) With this code, when i click on the button, the list shows up in the gnome panel : it's because I add it in the mainLayout. So how do I add it under the "gnome-panel". Thanks

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  • Google App Engine: Update model definitons?

    - by Rosarch
    I recently updated one of my models by adding a db.ListProperty(): class DependencyArcTail(db.Model): courses = db.ListProperty(db.Key) ''' newly added ''' forwardLinks = db.ListProperty(db.Key) However, I can't seem to get this to be reflected in the SDK dashboard. I cleared the datastore and reloaded it. Then I ran the procedures that create the DependencyArcTail objects. However, forwardLinks still doesn't show up as an attribute in the SDK dashboard. What's happening?

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  • Find all A^x in a given range

    - by Austin Henley
    I need to find all monomials in the form AX that when evaluated falls within a range from m to n. It is safe to say that the base A is greater than 1, the power X is greater than 2, and only integers need to be used. For example, in the range 50 to 100, the solutions would be: 2^6 3^4 4^3 My first attempt to solve this was to brute force all combinations of A and X that make "sense." However this becomes too slow when used for very large numbers in a big range since these solutions are used in part of much more intensive processing. Here is the code: def monoSearch(min, max): base = 2 power = 3 while 1: while base**power < max: if base**power > min: print "Found " + repr(base) + "^" + repr(power) + " = " + repr(base**power) power = power + 1 base = base + 1 power = 3 if base**power > max: break I could remove one base**power by saving the value in a temporary variable but I don't think that would make a drastic effect. I also wondered if using logarithms would be better or if there was a closed form expression for this. I am open to any optimizations or alternatives to finding the solutions.

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  • filter queryset based on list, including None

    - by jujule
    Hi all I dont know if its a django bug or a feature but i have a strange ORM behaviour with MySQL. class Status(models.Model): name = models.CharField(max_length = 50) class Article(models.Model) status = models.ForeignKey(status, blank = True, null=True) filters = Q(status__in =[0, 1,2] ) | Q(status=None) items = Article.objects.filter(filters) this returns Article items but some have other status than requested [0,1,2,None] looking at the sql query : SELECT [..] FROM `app_article` LEFT OUTER JOIN `app_status` ON (`app_article`.`status_id` = `app_status`.`id`) WHERE (`app_article`.`status_id` IN (1, 2) OR `app_status`.`id` IS NULL) ORDER BY [...] the OR app_status.id IS NULL part seems to be the cause. if i change it to OR app_article.status_id IS NULL it works correctly. How to deal with this ? Thanx.

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  • Writing a unique identifier to script?

    - by dannycab
    I'd like to write a subscript that adds a unique identifier (machine time) to a script everytime that it runs. However, each time I edit the script (in IDLE) the indetifiers are over-written. Is there a elegant way of doing this. The script that I wrote appears below. import os, time f = open('sys_time_append.py','r') lines = f.readlines() f.close() fout = open('sys_time_append.py','w') for thisline in lines: fout.write(thisline) fout.write('\n#'+str(time.time())+' s r\n') fout.close() Thanks for any help.

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  • Psycopg2 doesn't like table names that start with a lower case letter

    - by Count Boxer
    I am running ActiveState's ActivePython 2.6.5.12 and PostgreSQL 9.0 Beta 1 under Windows XP. If I create a table with an upper case first letter (i.e. Books), psycopg2 returns the "Programming Error: relation "books" does not exist" error message when I run the select statement: execute("SELECT * FROM Books"). The same error is returned if I run: execute("SELECT * FROM books"). However, if I change the table to a lower case first name (i.e. books), then either of the above statements works. Are tables name supposed to have a lower case first name? Is this a setting or a feature or a bug? Am I missing something obvious?

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  • Qt gstreamer problem

    - by ZolaKt
    Ptterb can you post your full code please? I copied your code. Added fvidscale_cap to pipeline, with: self.player.add(self.source, self.scaler, self.fvidscale_cap, self.sink) gst.element_link_many(self.source,self.scaler, self.fvidscale_cap, self.sink) From the main program I create a new QWidget, and pass its winId() to Vid constructor. The widget start loading, but crashes. The output says: should be playing Segmentation fault

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