Programmer blog

One comes to a task that has to do with counting items in a database. We will describe the right approach here. Despite being so obvious I did not find much of the docs for junior developers to watch and learn. Here is a sample task and solution: Let's assume we have a model like so: class Cycle (db.Model): id = db.Column(db.Integer, primary_key= True ) object_id = db.Column(db.String, nullable= False ) Sample date populated into it will be: { id : 1 , object_id: 'unique1' }, { id : 2 , object_id: 'unique1' }, { id : 3 , object_id: 'unique2' }, { id : 4 , object_id: 'unique2' }, { id : 5 , object_id: 'unique2' }, { id : 6 , object_id: 'unique3' } We need to count unique model instances with same  object_id . To achieve this relatively simple task one would go straightforward. E.g. Fetch all the Cycle instances with a simple query and then...

Upon development proces you often meet ManyToMany relations that throw errors in templates. I prefer to feed everything to context and play with it there. This kind of error appears when you iterate through a model's ManyToMany field. To fix it just add a related 'all' manager through dot syntax. Like so: Model: class BannerImage ( models . Model ) : image = models . ImageField ( upload_to = "somedir" ) def get_image_url ( self ) : return 'Image url here' class Banner ( models . Model ) : name = models . CharField ( max_length = 250 , null = True ) images = models . ManyToManyField ( BannerImage ) View/Tag or else, that creates context: banner = get_object_or_404 ( Banner , pk = 1 ) return { 'banner' : banner , } Template causing the error: {% for image in banner . images %} < img src = "{{ image.get_image_url }}" /> {% endfor %} Template without the error: {% ...

Today I had experience with django file downloads from an specified url into Django model FileField. I'm writing content grabber from Flickr. I didn't find information about it and decided to write what I've discovered so far in example. Stackoverflow helped me a bit. But answer proposed there had not worked. So this is code example how to workout this issue: because code worth a thousand words :) We have a model with one field: #models.py class Photo ( models . Model ):     image = models . ImageField ( 'Label' , upload_to = 'path/' ) We need to create a photo from image url and save it to the model's FileField. #somewhere in views.py # usually in header imports from urlparse import urlparse import urllib2 from django . core . files import File   #add imprt of content file wrapper from django . core . files . base import ContentFile # somewhere: for e.g. in view handling the file operations photo = Photo () img_url =...