5.7 KiB
Create Data with Many-to-Many Relationships
Let's continue from where we left and create some data.
We'll create data for this same many-to-many relationship with a link table:
We'll continue from where we left off with the previous code.
👀 Full file preview
{!./docs_src/tutorial/many_to_many/tutorial001.py!}
Create Heroes
As we have done before, we'll create a function create_heroes() and we'll create some teams and heroes in it:
# Code above omitted 👆
{!./docs_src/tutorial/many_to_many/tutorial001.py[ln:42-60]!}
# Code below omitted 👇
👀 Full file preview
{!./docs_src/tutorial/many_to_many/tutorial001.py!}
This is very similar to what we have done before.
We create a couple of teams, and then three heroes.
The only new detail is that instead of using an argument team we now use teams, because that is the name of the new relationship attribute. And more importantly, we pass a list of teams (even if it contains a single team).
See how Deadpond now belongs to the two teams?
Commit, Refresh, and Print
Now let's do as we have done before, commit the session, refresh the data, and print it:
# Code above omitted 👆
{!./docs_src/tutorial/many_to_many/tutorial001.py[ln:42-75]!}
# Code below omitted 👇
👀 Full file preview
{!./docs_src/tutorial/many_to_many/tutorial001.py!}
Add to Main
As before, add the create_heroes() function to the main() function to make sure it is called when running this program from the command line:
# Code above omitted 👆
{!./docs_src/tutorial/many_to_many/tutorial001.py[ln:78-80]!}
# Code below omitted 👇
👀 Full file preview
{!./docs_src/tutorial/many_to_many/tutorial001.py!}
Run the Program
If we run the program from the command line, it would output:
$ python app.py
// Previous output omitted 🙈
// Automatically start a new transaction
INFO Engine BEGIN (implicit)
// Insert the hero data first
INFO Engine INSERT INTO hero (name, secret_name, age) VALUES (?, ?, ?)
INFO Engine [generated in 0.00041s] ('Deadpond', 'Dive Wilson', None)
INFO Engine INSERT INTO hero (name, secret_name, age) VALUES (?, ?, ?)
INFO Engine [cached since 0.001942s ago] ('Rusty-Man', 'Tommy Sharp', 48)
INFO Engine INSERT INTO hero (name, secret_name, age) VALUES (?, ?, ?)
INFO Engine [cached since 0.002541s ago] ('Spider-Boy', 'Pedro Parqueador', None)
// Insert the team data second
INFO Engine INSERT INTO team (name, headquarters) VALUES (?, ?)
INFO Engine [generated in 0.00037s] ('Z-Force', 'Sister Margaret’s Bar')
INFO Engine INSERT INTO team (name, headquarters) VALUES (?, ?)
INFO Engine [cached since 0.001239s ago] ('Preventers', 'Sharp Tower')
// Insert the link data last, to be able to re-use the created IDs
INFO Engine INSERT INTO heroteamlink (team_id, hero_id) VALUES (?, ?)
INFO Engine [generated in 0.00026s] ((2, 3), (1, 1), (2, 1), (2, 2))
// Commit and save the data in the database
INFO Engine COMMIT
// Automatically start a new transaction
INFO Engine BEGIN (implicit)
// Refresh the data
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.id = ?
INFO Engine [generated in 0.00019s] (1,)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.id = ?
INFO Engine [cached since 0.001959s ago] (2,)
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age
FROM hero
WHERE hero.id = ?
INFO Engine [cached since 0.003215s ago] (3,)
// Print Deadpond
Deadpond: name='Deadpond' age=None id=1 secret_name='Dive Wilson'
// Accessing the .team attribute triggers a refresh
INFO Engine SELECT team.id AS team_id, team.name AS team_name, team.headquarters AS team_headquarters
FROM team, heroteamlink
WHERE ? = heroteamlink.hero_id AND team.id = heroteamlink.team_id
INFO Engine [generated in 0.00025s] (1,)
// Print Deadpond's teams, 2 teams! 🎉
Deadpond teams: [Team(id=1, name='Z-Force', headquarters='Sister Margaret’s Bar'), Team(id=2, name='Preventers', headquarters='Sharp Tower')]
// Print Rusty-Man
Rusty-Man: name='Rusty-Man' age=48 id=2 secret_name='Tommy Sharp'
// Accessing the .team attribute triggers a refresh
INFO Engine SELECT team.id AS team_id, team.name AS team_name, team.headquarters AS team_headquarters
FROM team, heroteamlink
WHERE ? = heroteamlink.hero_id AND team.id = heroteamlink.team_id
INFO Engine [cached since 0.001716s ago] (2,)
// Print Rusty-Man teams, just one, but still a list
Rusty-Man Teams: [Team(id=2, name='Preventers', headquarters='Sharp Tower')]
// Print Spider-Boy
Spider-Boy: name='Spider-Boy' age=None id=3 secret_name='Pedro Parqueador'
// Accessing the .team attribute triggers a refresh
INFO Engine SELECT team.id AS team_id, team.name AS team_name, team.headquarters AS team_headquarters
FROM team, heroteamlink
WHERE ? = heroteamlink.hero_id AND team.id = heroteamlink.team_id
INFO Engine [cached since 0.002739s ago] (3,)
// Print Spider-Boy's teams, just one, but still a list
Spider-Boy Teams: [Team(id=2, name='Preventers', headquarters='Sharp Tower')]
// Automatic roll back any previous automatic transaction, at the end of the with block
INFO Engine ROLLBACK
Recap
After setting up the model link, using it with relationship attributes is fairly straighforward, just Python objects. ✨