Using django for ParlimentAIry database

Currently this project contains a database in the db.sqlite3 file. This means the database information will exist locally and for updates to databases, you will need to pull for updated versions.

Database plan

A database contains data objects, instances that contain information from the website. Our parlimentAIry project contains one such database. A database can contain multiple tables. Each table lists a different type of object.

Included tables

For now, only a Question table is created. In django, tables are created through models and are constructed similarly to a python class in the file called models.py. In this project, you can find the file in the following directory:

website/q_answering/models.py

Planned tables

Later, we plan to add a table for:

• old questions
• articles

Creating a database table

Creating a database table is done in the following way:

• Add a new data object model to models.py
• Compile the code to update the database structure

Creating a model

For the exact syntax for the django models, I will refer you to the django documentation

Pointer: always include a __str__ function to make the object representation human readable.

Compile model to update table

After having written the code in models.py we can now make a migration:

python manage.py makemigrations q_answering

We can check the newest migration edits when we open the following folder in our editor:

website/q_answering/migrations/

When happy with all the migrations, we can 'build' the new table. This is when python uses sql to update our database structure:

python manage.py migrate

Accessing information from database

Accessing information from the database is now straightforward as we are using django, and can be done directly in python. It is somewhat similar to using python classes. Here I shall demonstrate how to work with database information using the already implemented Question model.

Accessing a table

This works similarly to importing local python files. This is necessary if you wish to have any sort of access to the table.

from q_answering.models import Question

Accessing rows from a table

We can query the database table through python, and ask the table to return a list with specific rows (objects) from a table.

Select all:

All question objects in table are returned in an iterable QuerySet

Question.objects.all()

Select with filter:

All question objects in table where the field 'status' has the value 'IP' are returned in an iterable QuerySet.

Question.objects.filter(status='IP')

Get a specific object:

If you want to retrieve a specific object from the table, and know for sure that your query will return exactly one object (e.g. because you query the primary key id), you can use the get method to return the object immediately:

Question.objects.get(pk=1)

Updating the database

Change field value

You can simply change the value of a field by assigning the new (valid) value to the attribute:

q = Question.objects.get(pk=1)
q.description = "hello world"

Add to table

To update this to the actual database, save it like so:

q.save()

Delete from table

To delete the entire entry from the database, delete it like so:

q.delete()