I'm trying to change values of a column in a table in a database at a specified time without having to do it manually. Is there a way to achieve this? If yes, wouldn't mind an example or something.
Thanks!! :)
ps. I'm using django with sqlite (using sqlite just because it comes with django as a default and I'm still learning django)
there are two ways to do
Install plugin for django scheduled tasks:django-chronograph.It should be really simple to create your schedule.
You will have to specify the linux command ./manage.py dbshell. Then use your query as parameter
Command reference: django-admin
Related
For my job interview, I got assignment to create CRUD with Django and Postgresql. I created database locally and finished my assignment.
Now I have to upload my code to github. The problem is, they asked for some exampled for CRUD. Developer that is reviewing my code obviously can't access my local DB.
What can I do to solve this issue? Do I have to upload my DB to cloud (if so what is the best way to do that)? Or is there any other way to resolve this?
Thanks in advance
When they download your code they would need to create their own local db, run python manage.py makemigrations and python manage.py migrate, then all the db tables will be created. However, there won't be any initial data.
I recommend downloading your code and running through every step it takes to get your project up and running. This would include things like create an admin user, etc. Then create a basic README with all the steps to make it as easy as possible for them to get it up and running.
Alternatively, you could Dockerize your application and provide a Dockerfile, but that's a bit overkill for a take home interview in my opinion. It may impress the interviewer nonetheless. They may not even want to download and run your project, just review your code in Github.
To provide initial data, you would want to look into writing fixtures. Then have them run python manage.py dumpdata to populate the db.
Just upload it to Heroku or something similar. You already have postgres as database so it's valid way. It is pretty straightforward with Heroku's official guide for django applications. I had same issue in my recruitment process and it was a solution that satisfied recruiter.
Database obviously will be empty unless you prepare some fixtures, which is very good idea. Django docs have something for that.
I would like to define a few PostgreSQL stored procedures in Django for later use, but I cannot find any support from Django to achieve this. I can do this by writing separate python script or SQL file, however I prefer to use Django migration feature. Anyone has done this before?
I have never used stored procedures with Django migration.
However, I am wondering: does it make sense? A stored procedure is not going to change your database schema in most of cases, therefore from my point of view you don't need to make a migration for it
I'm building a simple website with django that requires constant monitoring of text-based data from another website, that's the way it have to be.
How could I run this service on my web-host using django? would I have to start a separate app and run it via SSH, so it updates the database used by django, or are there any easier/better way?
You could use celery to schedule a job that would read data from that other website and do whatever you want with it.
As an alternative to celery, you could also create a cron job that executes a custom django-admin command. That would give you full access to your django install and ORM. The downside is that cron's smallest time resolution is 1 minute, so if you need it to be real-time, you're not going to be able to do that.
If you do need realtime, then creating a python daemon might be a better option.
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Possible Duplicate:
update django database to reflect changes in existing models
I've used Django in the past and one of the frustrations I've had with it as an ORM tools is the inability to update an existing database with changes in the model. (Hibernate does this very well and makes things really easy for updating and heavily modifying a model and applying this to an existing database.) Is there a way to do this without wiping the database every time? It gets really old having to regenerate admin users and sites after every change in the model which I'd like to play with.
You will want to look into South. It provides a migrations system to migrate both schema changes as well as data from one version to the next.
It's quite powerful and the vast majority of changes can be handled simple by going
manage.py schemamigration --auto
manage.py migrate
The auto functionality does have it limits, and especially if the change is going to be run on a production system eventually you should check the code --auto generated to be sure it's doing what you expect.
South has a great guide to getting started and is well documented. You can find it at http://south.aeracode.org
No.
As the documentation of syncdb command states:
Syncdb will not alter existing tables
syncdb will only create tables
for models which have not yet been installed. It will never issue
ALTER TABLE statements to match changes made to a model class after
installation. Changes to model classes and database schemas often
involve some form of ambiguity and, in those cases, Django would have
to guess at the correct changes to make. There is a risk that critical
data would be lost in the process.
If you have made changes to a model and wish to alter the database
tables to match, use the sql command to display the new SQL structure
and compare that to your existing table schema to work out the
changes.
South seems to be how most people solve this problem, but a really quick and easy way to do this is to change the db directly through your database's interactive shell. Just launch your db shell (usually just dbshell) and manually alter, add, drop the fields and tables you need changed using your db syntax.
You may want to run manage.py sqlall appname to see the sql statements Django would run if it was creating the updated table, and then use those to alter the database tables and fields as required.
The Making Changes to a Database Schema section of the Django book has a few examples of how to do this: http://www.djangobook.com/en/1.0/chapter05/
I manually go into the database - whatever that may be for you: MySQL, PostgreSQL, etc. - to change database info, and then I adjust the models.py accordingly for reference. I know there is Django South, but I didn't want to bother with using another 3rd party application.
How to make Django execute something automatically at a particular time.?
For example, my django application has to ftp upload to remote servers at pre defined times. The ftp server addresses, usernames, passwords, time, day and frequency has been defined in a django model.
I want to run a file upload automatically based on the values stored in the model.
One way to do is to write a python script and add it to the crontab. This script runs every minute and keeps an eye on the time values defined in the model.
Other thing that I can roughly think of is maybe django signals. I'm not sure if they can handle this issue. Is there a way to generate signals at predefined times (Haven't read indepth about them yet).
Just for the record - there is also celery which allows to schedule messages for the future dispatch. It's, however, a different beast than cron, as it requires/uses RabbitMQ and is meant for message queues.
I have been thinking about this recently and have found django-cron which seems as though it would do what you want.
Edit: Also if you are not specifically looking for Django based solution, I have recently used scheduler.py, which is a small single file script which works well and is simple to use.
I've had really good experiences with django-chronograph.
You need to set one crontab task: to call the chronograph python management command, which then runs other custom management commands, based on an admin-tweakable schedule
The problem you're describing is best solved using cron, not Django directly. Since it seems that you need to store data about your ftp uploads in your database (using Django to access it for logs or graphs or whatever), you can make a python script that uses Django which runs via cron.
James Bennett wrote a great article on how to do this which you can read in full here: http://www.b-list.org/weblog/2007/sep/22/standalone-django-scripts/
The main gist of it is that, you can write standalone django scripts that cron can launch and run periodically, and these scripts can fully utilize your Django database, models, and anything else they want to. This gives you the flexibility to run whatever code you need and populate your database, while not trying to make Django do something it wasn't meant to do (Django is a web framework, and is event-driven, not time-driven).
Best of luck!