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  • [Django] How to find out whether a model's column is a foreign key?

    - by codethief
    I'm dynamically storing information in the database depending on the request: // table, id and column are provided by the request table_obj = getattr(models, table) record = table_obj.objects.get(pk=id) setattr(record, column, request.POST['value']) The problem is that request.POST['value'] sometimes contains a foreign record's primary key (i.e. an integer) whereas Django expects the column's value to be an object of type ForeignModel: Cannot assign "u'122'": "ModelA.b" must be a "ModelB" instance. Now, is there an elegant way to dynamically check whether b is a column containing foreign keys and what model these keys are linked to? (So that I can load the foreign record by it's primary key and assign it to ModelA?) Or doesn't Django provide information like this to the programmer so I really have to get my hands dirty and use isinstance() on the foreign-key column?

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  • pitfalls with mixing storage engines in mysql with django?

    - by Dave Orr
    I'm running a django system over mysql in amazon's cloud, and the database default is innodb. But now I want to put a fulltext index on a couple of tables for searching, which evidently requires myisam. The obvious solution is to just tell mysql to ALTER TABLE to myisam, but are there going to be any issues with that? One that comes to mind is that I'll have to remember to do that any time I build a new version of the database, which should theoretically be rare, but there doesn't seem to be a way to tell django to please set the storage engine at the table level. I guess I could write a migration (we use south). Any other things I might be missing? What could possibly go wrong?

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  • How do I specify (1) an order and (2) a meaninful string representation for users in my Django application?

    - by David Faux
    I have a Django application with users. I have a model called "Course" with a foreign key called "teacher" to the default User model that Django provides: class Course(models.Model): ... teacher = models.ForeignKey(User, related_name='courses_taught') When I create a model form to edit information for individual courses, the possible users for the teacher field appear in this long select menu of user names. These users are ordered by ID, which is of meager use to me. How can I order these users by their last names? change the string representation of the User class to be "Firstname Lastname (username)" instead of "username"?

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  • concatenate multi values in one record without duplication

    - by mikehjun
    I have a dbf table like below which is the result of one to many join from two tables. I want to have unique zone values from one Taxlot id field. table name: input table tid ----- zone 1 ------ A 1 ------ A 1 ------ B 1 ------ C 2 ------ D 2 ------ E 3 ------ C Desirable output table table name: input table tid ----- zone 1 ------ A, B, C 2 ------ D, E 3 ------ C I got some help but couldn't make it to work. inputTbl = r"C:\temp\input.dbf" taxIdZoningDict = {} searchRows = gp.searchcursor(inputTbl) searchRow = searchRows.next() while searchRow: if searchRow.TID in taxIdZoningDict: taxIdZoningDict[searchRow.TID].add(searchRow.ZONE) else: taxIdZoningDict[searchRow.TID] = set() #a set prevents dulpicates! taxIdZoningDict[searchRow.TID].add(searchRow.ZONE) searchRow = searchRows.next() outputTbl = r"C:\temp\output.dbf" gp.CreateTable_management(r"C:\temp", "output.dbf") gp.AddField_management(outputTbl, "TID", "LONG") gp.AddField_management(outputTbl, "ZONES", "TEXT", "", "", "20") tidList = taxIdZoningDict.keys() tidList.sort() #sorts in ascending order insertRows = gp.insertcursor(outputTbl) for tid in tidList: concatString = "" for zone in taxIdZoningDict[tid] concatString = concatString + zone + "," insertRow = insertRows.newrow() insertRow.TID = tid insertRow.ZONES = concatString[:-1] insertRows.insertrow(insertRow) del insertRow del insertRows

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  • Really basic Django E-commerce? Where do I start

    - by Andrew
    I'm trying to set up a really basic e-commerce site with Django, and am trying to figure out the best place to start. I am relatively comfortable with the framework itself, but have never done any sort of e-commerce development in any language, so I want to learn about some best practices so I don't make any huge or obvious mistakes. I've looked at Satchmo, and even went as far as installing and playing around with it, but it looks like way more than I want. I basically want to show users a list of things, and let them click a button to buy one. No cart, no shipping, just click a button, connect with Authorize.net (or something similar) to do the transaction, and then display a confirmation page. Any suggestions or online tutorials people have found helpful? Even perhaps a tutorial in another language. Or maybe a really lightweight Django plugin that doesn't try to do everything like Satchmo? I've been coming up with very little so far. Thanks!

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  • Turbogears 2 vs Django - any advice on choosing replacement for Turbogears 1?

    - by michela
    I have been using Turbogears 1 for prototyping small sites for the last couple of years and it is getting a little long in the tooth. Any suggestions on making the call between upgrading to Turbogears 2 or switching to something like Django? I'm torn between the familiarity of the TG community who are pretty responsive and do pretty good documentation vs the far larger community using Django. I am quite tempted by the built-in CMS features and the Google AppEngine support. Any advice? Thanks .M.

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  • How do I construct a Django form with model objects in a Select widget?

    - by Thierry Lam
    Let's say I'm using the Django Site model: class Site(models.Model): name = models.CharField(max_length=50) My Site values are (key, value): 1. Stackoverflow 2. Serverfault 3. Superuser I want to construct a form with an html select widget with the above values: <select> <option value="1">Stackoverflow</option> <option value="2">Serverfault</option> <option value="3">Superuser</option> </select> I'm thinking of starting with the following code but it's incomplete: class SiteForm(forms.Form): site = forms.IntegerField(widget=forms.Select()) Any ideas how I can achieve that with Django form?

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  • Is it possible to use Django's testing framework without having CREATE DATABASE rights?

    - by superjoe30
    Since I don't have a hundred bazillion dollars, my Django app lives on a shared host, where all kinds of crazy rules are in effect. Fortunately, they gave me shell access, which has allowed me to kick butts and take names. However I can't do anything about not having CREATE DATABASE rights. I'm using postgresql and have a killer test suite, but am unable to run it due to the code not being able to create a new database. However I am able to create said database beforehand via cPanel and use it with Django. I just don't have CREATE DATABASE rights. Is there a way I can still run my test suite?

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  • Connect to a DB with an encrypted password with Django?

    - by Liam
    My place of employment requires that all passwords must be encrypted, including the ones used to connect to a database. What's the best way of handling this? I'm using the development version of Django with MySQL at the moment, but I will be eventually migrating to Oracle. Is this a job for Django, or the database? Edit: The encrypted password should be stored in the settings.py file, or somewhere else in the filesystem. This is the password that will be used to connect to the database.

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  • Why would Django fcgi just die? How can I find out?

    - by Joe
    I'm running Django on Linux using fcgi and Lighttpd. Every now and again (about once a day) the server just dies. I'm using the latest stable release of Django, Python and Lighttpd. The only thing I can think of is that my program is opening a lot of files and executing a lot of external processes, but I'm fairly sure that side of things is watertight. Looking at the error and access logs, there's nothing exceptional happening (i.e. load isn't above normal). On those occasions where I have had exceptions from Python, these have shown up in the error.log, but when this crash happens I get nothing. Is there any way of finding out why the process died? Short of putting logging statements on every single line? Obviously I can't reproduce this so I don't know exactly where to look.

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  • How painful is a django project upload to a live (staging) site?

    - by Ignacio
    Hi, I've getting quite fast with a small django project of mine, which I'm developing locally, of course. But, as I had never worked with django before, I'm not aware of what it implies to upload it and test it on a production server. And I'm quite curious, since I'm very eager to test an early release live. I know there is this document, which I think it'll be really helpful: http://djangobook.com/en/2.0/chapter12/ But, are there any details I should take into account before, during and after the deployment? Any advice or best practices? Thanks.

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  • How to start doing TDD in a django project?

    - by Satoru.Logic
    Hi, all. I have read a lot of essays talking about benifits TDD can bring to a project, but I have never practiced TDD in my own project before. Now I'm starting an experimental project with Django, and I think maybe I can have a try of TDD. But what I find now is that I don't even know how to answer the question "what should I put in my test cases?". Please tell me how should I plan TDD in a project, in this case, a web project based on Django. Thanks.

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  • Django: do I need to do HttpResponseRedirect to render a simple string after a POST?

    - by AP257
    I've got a mobile app that makes POST requests to a Django site. I want to return a simple string (not a template-based page) after the app makes the POST request, saying 'Success' or 'Failure' as appropriate. However I know that after a POST request in Django you're supposed to do a HttpResponseRedirect. But, do I really need to redirect to another page and write a new function to handle it, all to output a string? And if so, how do I pass the success/failure status of the app in the HttpResponseRedirect, since it's only supposed to take one argument? Thanks!

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  • How do I point a domain name to a Django url?

    - by username2
    I have a subdomain m.example.com that I want to point to the same location as example.com/mobile running on an apache2/django1.3 installation. example.com is the landing page, and I have the urls.py configured such that urls that match /^mobile$/ will be served the mobile version of the page. I looked into <VirtualHost>, but I think it requires a physical location for me to point m.example.com at and with the django urls there is no physical location except for the root of the project directory. I am unsure if the configuration change is made on the apache side or the django side. I've also looked into the mod_rewrite module for Apache, but I would prefer if I didnt have to redirect m.example.com to example.com/mobile

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  • How painful is a django project deployment to a live (staging) site?

    - by Ignacio
    Hi, I've getting quite fast with a small django project of mine, which I'm developing locally, of course. But, as I had never worked with django before, I'm not aware of what it implies to upload it and test it on a production server. And I'm quite curious, since I'm very eager to test an early release live. I know there is this document, which I think it'll be really helpful: http://djangobook.com/en/2.0/chapter12/ But, are there any details I should take into account before, during and after the deployment? Any advice or best practices? Thanks.

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  • How to select random image of specific size using Django / Python?

    - by Jonathan
    I've been using this little snippet to select random images. However I would like to change it to select only images of a certain size. I'm running into trouble checking against image size. If I use get_image_dimensions() I need to use a conditional statement, which then requires that I allow exceptions. So, I guess I need some pointers on just limiting by image dimensions. Thanks. import os import random import posixpath from django import template from django.conf import settings register = template.Library() def is_image_file(filename): """Does `filename` appear to be an image file?""" img_types = [".jpg", ".jpeg", ".png", ".gif"] ext = os.path.splitext(filename)[1] return ext in img_types @register.simple_tag def random_image(path): """ Select a random image file from the provided directory and return its href. `path` should be relative to MEDIA_ROOT. Usage: <img src='{% random_image "images/whatever/" %}'> """ fullpath = os.path.join(settings.MEDIA_ROOT, path) filenames = [f for f in os.listdir(fullpath) if is_image_file(f)] pick = random.choice(filenames) return posixpath.join(settings.MEDIA_URL, path, pick)

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  • Django Custom Field: Only run to_python() on values from DB?

    - by Adam Levy
    How can I ensure that my custom field's *to_python()* method is only called when the data in the field has been loaded from the DB? I'm trying to use a Custom Field to handle the Base64 Encoding/Decoding of a single model property. Everything appeared to be working correctly until I instantiated a new instance of the model and set this property with its plaintext value...at that point, Django tried to decode the field but failed because it was plaintext. The allure of the Custom Field implementation was that I thought I could handle 100% of the encoding/decoding logic there, so that no other part of my code ever needed to know about it. What am I doing wrong? (NOTE: This is just an example to illustrate my problem, I don't need advice on how I should or should not be using Base64 Encoding) def encode(value): return base64.b64encode(value) def decode(value): return base64.b64decode(value) class EncodedField(models.CharField): __metaclass__ = models.SubfieldBase def __init__(self, max_length, *args, **kwargs): super(EncodedField, self).__init__(*args, **kwargs) def get_prep_value(self, value): return encode(value) def to_python(self, value): return decode(value) class Person(models.Model): internal_id = EncodedField(max_length=32) ...and it breaks when I do this in the interactive shell. Why is it calling to_python() here? >>> from myapp.models import * >>> Person(internal_id="foo") Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/base.py", line 330, in __init__ setattr(self, field.attname, val) File "/usr/local/lib/python2.6/dist-packages/django/db/models/fields/subclassing.py", line 98, in __set__ obj.__dict__[self.field.name] = self.field.to_python(value) File "../myapp/models.py", line 87, in to_python return decode(value) File "../myapp/models.py", line 74, in decode return base64.b64decode(value) File "/usr/lib/python2.6/base64.py", line 76, in b64decode raise TypeError(msg) TypeError: Incorrect padding I had expected I would be able to do something like this... >>> from myapp.models import * >>> obj = Person(internal_id="foo") >>> obj.internal_id 'foo' >>> obj.save() >>> newObj = Person.objects.get(internal_id="foo") >>> newObj.internal_id 'foo' >>> newObj.internal_id = "bar" >>> newObj.internal_id 'bar' >>> newObj.save() ...what am I doing wrong?

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  • django: how to use many-to-many relationships in values()?

    - by john
    i need to group results by a field that requires a few joins from the original model: // response_filter_args is created dynamically responses = Response.objects.filter(**response_filter_args) \ .values('customer__tags__tag') \ # django doesn't like this .annotate(average_score=Avg('rating__score')) Response - customer - tags (many-to-many field pointing to Tag) - tag (the tag as a string) Models are: class Response(models.Model): customer = models.ForeignKey(Customer) ... class Customer(models.Model): tags = models.ManyToManyField(Tag) ... class Tag(models.Model): tag = models.CharField(max_length=255) ... i'm trying to calculate average ratings. to make it work i need to tell django to group by 'tag', but it refuses to. it gives an error: Invalid field name: 'customer__tags__tag' anyone know how i can get it to group by tag? i've tried all the combinations of underscores in customer_tags_tag that i can think of, but nothing works.

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  • tcpdf table header in each page

    - by DragoN
    i am using tcpdf to create pdf files with rows of table in the first page of pdf i display some info like : List of table .... and header of table after that i display the rows in table if there much rows it contiunes in the next page without the info [List of table... and header of table] i want to display the header of table only in the next pages here is my code $pdf->SetFont('aefurat', '', 15); $pdf->AddPage('P', 'A4'); $pdf->SetFontSize(17); $pdf->Cell(0, 13, 'List of the Byan Table,'C'); $pdf->SetFont('dejavusans', '', 14); $htmlpersian = 'In / Out List'; $pdf->WriteHTML($htmlpersian, true, 0, true, 0); $pdf->setRTL(false); $pdf->SetFontSize(11); $pdf->setRTL(true); Connect(); $resultsc = mysql_query("SELECT * FROM byan Order By Date "); while($r = mysql_fetch_array($resultsc)) { $printresult .= ' <tr> <td ><center>'.$r['Date'].'</center></td> <td ><center>'.$r['In'].'</center></td> <td ><center>'.$r['Out'].'</center></td> <td ><center>'.$r['Balance'].'</center></td> <td ><center>'.$r['Info'].'</center></td> <td ><center>'.$r['Number'].'</center></td> </tr>'; } $tbl = ' <table cellspacing="0" cellpadding="1" border="1" align="center"> <tr> <td style="width: 13%; background-color:black; color:white;"><center>Date</center></td> <td style="width: 11%; background-color:black; color:white;"><center>In</center></td> <td style="width: 11%; background-color:black; color:white;"><center>Out</center></td> <td style="width: 12%; background-color:black; color:white;"><center>Balance</center></td> <td style="width: 45%; background-color:black; color:white;"><center>Info</center></td> <td style="width: 11%; background-color:black; color:white;"><center>Number</center></td> </tr> '.$printresult.' </table> '; $pdf->writeHTML($tbl, true, false, true, false, ''); the output is First Page: List of the Byan Table In / Out List Table Header rows Second Page: Rows Third Page: Rows i want the output to be like that First Page: List of the Byan Table In / Out List Table Header Rows Second Page: Table Header Rows Third Page: Table Header Rows

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  • Joins in single-table queries

    - by Rob Farley
    Tables are only metadata. They don’t store data. I’ve written something about this before, but I want to take a viewpoint of this idea around the topic of joins, especially since it’s the topic for T-SQL Tuesday this month. Hosted this time by Sebastian Meine (@sqlity), who has a whole series on joins this month. Good for him – it’s a great topic. In that last post I discussed the fact that we write queries against tables, but that the engine turns it into a plan against indexes. My point wasn’t simply that a table is actually just a Clustered Index (or heap, which I consider just a special type of index), but that data access always happens against indexes – never tables – and we should be thinking about the indexes (specifically the non-clustered ones) when we write our queries. I described the scenario of looking up phone numbers, and how it never really occurs to us that there is a master list of phone numbers, because we think in terms of the useful non-clustered indexes that the phone companies provide us, but anyway – that’s not the point of this post. So a table is metadata. It stores information about the names of columns and their data types. Nullability, default values, constraints, triggers – these are all things that define the table, but the data isn’t stored in the table. The data that a table describes is stored in a heap or clustered index, but it goes further than this. All the useful data is going to live in non-clustered indexes. Remember this. It’s important. Stop thinking about tables, and start thinking about indexes. So let’s think about tables as indexes. This applies even in a world created by someone else, who doesn’t have the best indexes in mind for you. I’m sure you don’t need me to explain Covering Index bit – the fact that if you don’t have sufficient columns “included” in your index, your query plan will either have to do a Lookup, or else it’ll give up using your index and use one that does have everything it needs (even if that means scanning it). If you haven’t seen that before, drop me a line and I’ll run through it with you. Or go and read a post I did a long while ago about the maths involved in that decision. So – what I’m going to tell you is that a Lookup is a join. When I run SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 285; against the AdventureWorks2012 get the following plan: I’m sure you can see the join. Don’t look in the query, it’s not there. But you should be able to see the join in the plan. It’s an Inner Join, implemented by a Nested Loop. It’s pulling data in from the Index Seek, and joining that to the results of a Key Lookup. It clearly is – the QO wouldn’t call it that if it wasn’t really one. It behaves exactly like any other Nested Loop (Inner Join) operator, pulling rows from one side and putting a request in from the other. You wouldn’t have a problem accepting it as a join if the query were slightly different, such as SELECT sod.OrderQty FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail as sod on sod.SalesOrderID = soh.SalesOrderID WHERE soh.SalesPersonID = 285; Amazingly similar, of course. This one is an explicit join, the first example was just as much a join, even thought you didn’t actually ask for one. You need to consider this when you’re thinking about your queries. But it gets more interesting. Consider this query: SELECT SalesOrderID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276 AND CustomerID = 29522; It doesn’t look like there’s a join here either, but look at the plan. That’s not some Lookup in action – that’s a proper Merge Join. The Query Optimizer has worked out that it can get the data it needs by looking in two separate indexes and then doing a Merge Join on the data that it gets. Both indexes used are ordered by the column that’s indexed (one on SalesPersonID, one on CustomerID), and then by the CIX key SalesOrderID. Just like when you seek in the phone book to Farley, the Farleys you have are ordered by FirstName, these seek operations return the data ordered by the next field. This order is SalesOrderID, even though you didn’t explicitly put that column in the index definition. The result is two datasets that are ordered by SalesOrderID, making them very mergeable. Another example is the simple query SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276; This one prefers a Hash Match to a standard lookup even! This isn’t just ordinary index intersection, this is something else again! Just like before, we could imagine it better with two whole tables, but we shouldn’t try to distinguish between joining two tables and joining two indexes. The Query Optimizer can see (using basic maths) that it’s worth doing these particular operations using these two less-than-ideal indexes (because of course, the best indexese would be on both columns – a composite such as (SalesPersonID, CustomerID – and it would have the SalesOrderID column as part of it as the CIX key still). You need to think like this too. Not in terms of excusing single-column indexes like the ones in AdventureWorks2012, but in terms of having a picture about how you’d like your queries to run. If you start to think about what data you need, where it’s coming from, and how it’s going to be used, then you will almost certainly write better queries. …and yes, this would include when you’re dealing with regular joins across multiples, not just against joins within single table queries.

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  • Learning PostgreSql: old versions of rows are stored right in the table

    - by Alexander Kuznetsov
    PostgreSql features multi-version concurrency control aka MVCC. To implement MVCC, old versions of rows are stored right in the same table, and this is very different from what SQL Server does, and it leads to some very interesting consequences. Let us play with this thing a little bit, but first we need to set up some test data. Setting up. First of all, let us create a numbers table. Any production database must have it anyway: CREATE TABLE Numbers ( i INTEGER ); INSERT INTO Numbers ( i ) VALUES...(read more)

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