I have a Django site that is up and running. I need to add a feature to call wget in response to a user action. How should I do this from the Django application?
Since Django is written in Python you can use Python's subprocess module to call wget in one of your views. However, if you merely want to download a file with wget (and not use one of its advanced features), you can emulate its behavior more easily with urllib2.
Is there a reason why you're resorting to a unix command, rather than using something like urllib2?
If there is, you can always use this within your view:
from subprocess import call
call(["wget", "http://myurl.com"])
Here's a pretty comprehensive thread on the matter:
Calling an external command in Python
Use Celery
Related
My Django application called my_app pulls in a dependency called my_dependency.
my_dependency declares a management command called useful_thing
Is there a way I can run useful_thing directly from my_app's start.sh?
I've tried calling it directly but it's not found, but maybe there's a way I can configure it to look for management commands from a particular place? I'm new to Django and suspect this is not a sensible thing to try and do.
You can call any (properly defined) management command using Django's manage.py, just like any other Django command:
python manage.py userful_thing
Django 3.0 is adding asgi / async support and with it a guard around making synchronous requests in an async context. Concurrently, IPython just added top level async/await support, which seems to be running the whole interpreter session inside of a default event loop.
Unfortunately the combination of these two great addition means that any django ORM operation in a jupyter notebook causes a SynchronousOnlyOperation exception:
SynchronousOnlyOperation: You cannot call this from an async context - use a thread or sync_to_async.
As the exception message says, it's possible to wrap each ORM call in a sync_to_async() like:
images = await sync_to_async(Image.objects.all)()
but it's not very convenient, especially for related fields which would usually be implicitly resolved on attribute lookup.
(I tried %autoawait off magic but it didn't work, from a quick glance at the docs I'm assuming it's because ipykernels always run in an asyncio loop)
So is there a way to either disable the sync in async context check in django or run an ipykernel in a synchronous context?
For context: I wrote a data science package that uses django as a backend server but also exposes a jupyter based interface on top of the ORM that allows you to clean/annotate data, track machine learning experiments and run training jobs all in a jupyter notebook.
It works for me
os.environ["DJANGO_ALLOW_ASYNC_UNSAFE"] = "true"
BTW, I start my notebook using the command
./manage.py shell_plus --notebook
Contrary to other answers I'd suggest just running from the shell as:
env DJANGO_ALLOW_ASYNC_UNSAFE=true ./manage.py shell_plus --notebook
and not modifying any config files or startup scripts.
The advantage of doing it like this is that these checks still seem useful to have enabled almost everywhere else (e.g. when debugging locally via runserver or when running tests). Disabling via files would easily disable these in too many places negating their advantage.
Note that most shells provide easy ways of recalling previously invoked command lines, e.g. in Bash or Zsh Ctrl+R followed by notebook would find the last time you ran something that had "notebook" in. Under the fish shell just type notebook and press the up arrow key to start a reverse search.
For now I plan on just using a forked version of django with a new setting to skip the async_unsafe check. Once the ORM gets async support I'll probably have to rewrite my project to support it and drop the flag.
EDIT: there's now a PR to add an env variable (DJANGO_ALLOW_ASYNC_UNSAFE) to disable the check (https://github.com/django/django/pull/12172)
I added
os.environ["DJANGO_ALLOW_ASYNC_UNSAFE"] = "true" code in the setting.py of your project all the way down to the file and then
command python3 manage.py shell_plus --notebook
if you are using python3 or use python
That's it. worked for me.
What i have done?
I have written a small application in django with few models with sqlite3 as backend. Now i want to write a python code that clears the database elements based on certain condition.
Question:
How can i achieve the above requirement?
I think the cleanest way to do this is to write your own django-admin command.
You can then run the command using manage.py:
python manage.py your_command
Having a command that can be run in shell, you can easily put in into your crontab. Optionally django-admin commands can receive command line arguments, if needed.
I'm trying to write a custom command that works outside of Django projects. I was thinking I could follow the coding patterns of Django's own such commands (e.g., startproject), include my command in an app and install it.
Alas, it seems django cannot see this command, as perhaps it doesn't scan site-packages for custom commands.
Is there a way to make this work or am I sadly correct?
UPDATE: I should note that the goal I was trying to accomplish (writing a command that starts projects based on custom templates) is supported in the coming 1.4 release of Django: https://docs.djangoproject.com/en/dev/ref/django-admin/#django-admin-startproject (see the --template option).
Based on this code from django.core.management, it does appear that django only searches for project-less commands in its own packages, and will then only find command by scanning INSTALLED_APPS, which means a project is required.
You can use a custom manage.py.
You do need a project. A project is, although, nothing more than a python package with a settings.py (and maybe a urls.py file)
So you could just create a project, with whatever commands you want, and in your setup script include a binary script that is nothing more than a manage.py in disguise.
I use it to have a manage.py in the bin path of a virtualenv, but you can call it something else and have that "django" project installed in your system python.
I don't quite understand from your post, for what purpose do You want to write such command using Django's manage.py. But suppose you want (as I was) to run some script, that works with Django models, for example. You cannot run such script without setting Django environment.
I do the following:
put my code in script.py
manage.py shell
execfile('script.py')
Maybe, this helps.
Ipython has a plugin called autoreload that will presumably reload all your modules after every command, so you can change the source and not have to quit the shell and reenter all your commands. See http://dsnra.jpl.nasa.gov/software/Python/tips-ipython.html for example.
However, this seems flaky at best when using it with Django, e.g.
python manage.py shell
gives me an IPython shell with Django context, but the autoreloading does NOT seem to work reliably at all.
Here's what I have added to my ipy_user_conf.py file:
def main():
... # rest of the fn here
import ipy_autoreload
ip.magic('%autoreload 2')
The autoreloading works in limited cases, maybe 10-20% of the time.
Has anyone successfully configured this to work with Django?
This answer might also be applicable to your situation. Django keeps its own cache of all models, so if you want to reload everything, you have to clean this cache manually.