OK -- I've been working with Django for a few months now and have come across a weird issue. To set it up, here's my webapp structure.
The main Django project is called cpm.
I have a bunch of django apps in the cpm folder. Within each app, I have my models.py file.
Now, when I want to create/use models from other apps I would do something like:
from cpm.products.models import *
assuming an app named products was present. Recently, I started to get some errors saying things like, cannot import XYZ from products. So, after much searching, I changed the line:
from cpm.products.models import *
to
from products.models import *
I just dropped the cpm. part and now it works.
Can someone tell me why this is happening? It seems to be happening on only portions of my apps (I have a bunch within the CPM project). I want to make sure my syntax is accurate as I move forward.
Thanks!
The project root's directory got removed from the python path somewhere along the way, or you removed the __init__.py file from it's root.
On a side note, importing * will lead to issues, especially when you start adding lots of apps. Consider doing from products import models as prod_models. Then doing prod_models.MyModel where you need to reference your models.
Related
I have a few defined apps in my Django project, each with their own sub-directory (created with startapp)
In the views.py of app1 I have an import to a model from app2
from app2.models import MyModel
This worked in Django 1.6.x. In version 1.9 I get:
Could not resolve variable
sometimes on MyModel, sometimes on the filter(..) method, or on both.
If I change the import to
from app2.models import * ##UnusedWildImport
then everything works just fine.
Has anything changed in 1.9.x (or before) that requires a different mode of importing models external to the app?
I think I can rule our circular import problems as this would have failed in 1.6...
Edit: Based on the comments I started wondering whether this might be a PyDev problem.
I tried:
Removing and re-adding Python to PyDev - it did not help
This https://stackoverflow.com/a/8534599/5958359 - removing the myproject/src folder from PYTHONPATH worked ... with a caveat.
The error did not appear when I completely removed the import statement, so this is not a good solution
This is a PyDev error.
Searches haven't yielded an adequate solution - most simply explain how to disable the error - so I will not link to any solution here.
My workaround, as much as I don't like from xxx import * seems like the best temporary solution.
I am new to Django and have a little problem with making all the project structure clear and organized and so on.. The MVC stuff in Django is quite easy to use when making a small project. However, when I am trying to get a new layer (application logic, like three-tier architecture) between views.py and models.py I have problem to do so.
I have the following structure:
mysite/
manage.py
app1/
models.py
views.py
logic/
__init__.py
Class1.py
parser.py
...
and I want to load into views.py stuff from Class1.py and parser.py.
How do I do it?
Neither of the following works:
from app1.logic import *
from app1.logic.Class1 import Class1
Also, it would help me if somebody could list me some example of a really huge django project. It looks like either lots of classes and .py files should be in every app folder or everything is in the models.py.. Both look a little disorganised and I'm sure there is a way to make it a little bit clearer (like in Zend or Symfony).
And, I'm working with Python3 and Django 1.5b2.
Thanks.
If Class1 or parser import from views, then you have a circular dependency. You'll need to move any shared code out into a third file.
You might consider though whether you need all those separate files under logic. In Python there's no requirement to have a class in its own file, so maybe you could have a single logic.py instead of a logic directory containing several files.
i am trying django-selectable the 'fruit' example given in the docs here -
https://django-selectable.readthedocs.org/en/version-0.6.2/quick-start.html#defining-a-lookup
getting LookupAlreadyRegistered error,there is a small note on this error,but i can't
figure out how to solve this.i understand that it has something to do with import statements, i am using django-1.3
i will provide more info if needed , but i am just using the same code as given in the example.
kindly help
Check the note in the link you've posted:
You should only register your lookup once. Attempting to register the same lookup class more than once will lead to LookupAlreadyRegistered errors. A common problem related to the LookupAlreadyRegistered error is related to inconsistant import paths in your project. Prior to Django 1.4 the default manage.py allows for importing both with and without the project name (i.e. from myproject.myapp import lookups or from myapp import lookups). This leads to the lookup.py file being imported twice and the registration code executing twice. Thankfully this is no longer the default in Django 1.4. Keeping your import consistant to include the project name (when your app is included inside the project directory) will avoid these errors.
I like Eclipse for a number of reasons. One of them is, when I'm doing a java project, I can copy and paste my project or rename it, to make a new one, and it will update all the names of everything.
I'm trying to do something similar for a django project.
I can set an APPNAME variable with the following code
APPNAME = os.path.basename(os.path.dirname(__file__))
and then I could import this in any file that needed to know the name of the application. This isn't an ideal solution however but it would work for my settings.py file as well as my urls.py files.
It won't work for situations where I need to import something from somewhere like so:
from myproject.someapp import forms
Is there a way for django/python to know what "myproject" is? Or can I use an import statement relative to the current app?
Or maybe there's a better way to copy django projects.
EDIT: I imagine there are also database dependencies as well that I'd have to deal with.
I follow a couple of rules to keep my applications portable. I'll list them below in the hope that someone finds them useful.
Include my apps in the PYTHONPATH rather than my projects. This way I can execute from app import forms rather than from project.app ....
Following #1, I always import from app only. This means I can reuse my apps in other projects without having to change import statements within the app or in other dependent apps.
If you stick to #1 and #2 you can generally copy and paste projects without too much trouble. You'll still have to modify settings.py though.
I've been doing a little clean up on my django project and so I decided to rename some models remove some unnecessary fields etc. I dropped all the tables from the dbase and reran "syncdb". However, now I'm getting and error
Could not import pollsite.polls.views. Error was: cannot import name OldTableName
Its a template error from base.html
OldTableName doesn't exist anymore (I've renamed it). Is there something else I need to run to get the admin site to work properly with the new schema?
You need to check your imports in your pollsite.polls.views. Most likely you still have an import of the old model name in that file.