How can I create an application scope variable which is loaded when the django app starts, be in memory and accessible by all.
Basically I want to reuse the variable through out the application without reloading it.
Thanks
You could add it to your settings.py file. Or, add it to the __init__.py file inside the app directory.
Are you referring to something like an environment variable? You could load it via init...
__init__.py
import os
os.environ['APP_VAR_WHATEVER'] = 'hello world!'
Python has three levels of namespace — local (specific to the current function or class method), global (specific to the current module), and built-in. That is, Python does not really have project-wide global variables.
If it's a read-only variable you want, you could use settings.py to define the value and import settings from all other modules that want access to the variable.
If it for both reading and writing, I would likely use the database backend I'm already using with Django, instead of a python variable.
If you could provide a more detailed description of what you're trying to achieve, perhaps we could come up with a better suited solution.
Related
Suppose I have some global settings for my Django project, stored in a text file for easy editing. I want to load the settings, and then store these variables such that they are accessible from any of my view functions. However, I have read that global variables in Django are discouraged. So, how should I do it? I know how to store these variables in a database, but this seems overkill just for storing a few simple variables.
As alecxe has already pointed out, you can use the settings system. This is the customary way to set values that must be used project-wide. If you read the documentation I've linked too you'll see that they cover very early on that page how to set your own settings.
One thing you must not do when you use Django's settings system is refer to settings at the top level of your modules. For instance if you have a view that does this:
from django.conf import settings
FOO = settings.FOO
(Or alecxe's print statement.) This will prevent values from being overriden. The documentation here goes over the details. I recall having had problems in testing due to this because some of my tests were trying to override the default values, and failed.
The settings system I've mentioned above should be used for values that are meant to be set at start up and not changed afterwards. If you want to record settings that can be changed by the site's administrator at run time, you should use a database of some sort.
Just store your variables in settings.py, this is the best and preferrable way to store your project-specific settings. Then, you can always access them by importing django.conf.settings:
from django.conf import settings
print settings.MY_SETTING
Hope that helps.
I am working on a django app that needs a directory to download and store files.
I want to keep my app reusable so I do not want to hard code the path of this directory.
So I want to make this path a setting/a global variable that can be set up.
Where could I put this setting/global variable?
Is this kind of approach good ?
http://blog.muhuk.com/2010/01/26/developing-reusable-django-apps-app-settings.html
Thanks for your advice!
I use the following methodology:
# some file in your app:
from django.conf import settings
MY_APP_SETTING = getattr(settings, 'MY_APP_SETTING', 'some default value')
This effectively allows end-users to customized the setting in their own settings.py, but still ensures that there's always some default value set. You can now use MY_APP_SETTING at will in the rest of your code.
UPDATE
The link in your question was taking too long to load, so I just went ahead and answered. As it turns out, the method I suggested is the same as what it suggests, so yes, I'd consider that approach good ;).
I have an application that requires the user to have a certain directory structure much like django does with templatetags and what I would like to know is how do I import an application named foo from a django project at runtime?
Furthermore if the application exists how do I import a specific module of application foo?
I think your question requires a few clarifying details. At the moment it seems as simple as putting the application (do you mean a django application?) on your pythonpath (e.g. inside the project directory):
try:
import foo
except ImportError:
pass # application mustn't be on pythonpath
else:
from foo import specific_module
# do stuff
Depending on your requirements, this code could be in a view, or even your project's __init__.py if you want it to happen quite early. Improvements to django's start-up process are coming soon -- keep an eye out for startup.py features.
If you need to import modules with dynamic names, you might want to look into __import__
You also have an helper method within django that is called django.utils.importlib.import_module (which uses __import__)
I have a bunch of functions that I created in some views that must be reused in many other views. Do I need to create a class and put those functions in a class? If yes how exactly has to be done in Django and then how do I call and initiate them in the new views?
Django views are just Python functions. You can call other Python functions from them just as you can from any other Python code. Put your functions into a .py file, import it, and invoke the functions.
Of course, it may make sense for other reasons to create a class to hold the functions, but you certainly don't need to in order to call them from views.
The solution would be to create the myfunctions.py file in your app folder and import it in your views. Your views file would look like:
import myfunctions
def my_view(request):
.....
foo = myfunctions.bar()
....
You look to complicated to Django. Django is just another Python application and lives in the Python world. For example you can create file library.py and import this file where is needed (in modules where the function from library is needed). If you need you library's functions to get data from database, just import models in the library.py and use them.
Django doesn't have such a big think as "module". You creating the architecture, you can define what in your case is module. In general this is just simple directory with init.py file inside to be able to import files from there.
Hope that helped.
From my point of view, if you have a lot of functions that are widely used in your project it make sense put all this in some separate application. I create some module named 'contrib' for this purposes. It can avoid some time for maintaining this code in future
I am working on a Django app and I have a class which reads the contents of a file and returns a Django model. My question is where do I store this class in the file system? All this does is reads the file, populates a Django model and returns it.
Thanks
There is nothing special about a Django application: it's just a Python package. Technically you can put the class anywhere you can import.
With that being said, it's best to keep related code bundled together. It sounds like a good place for this particular class is in the file that declares the Model it returns.
On the other hand it might be logical to throw it into the application's __init__.py file.
You could also make a utils, etc, admin, scripts . . . folder/package to put utility classes and scripts if it's meant to be used for administration and site maintenance.
In the end it's more about how you want to organize your project, but technically it can live just about anywhere.