How Can I Automatically Populate SQLAlchemy Database Fields? (Flask-SQLAlchemy)

Question

I've got a simple User model, defined like so:

# models.py from datetime import datetime from myapp import db  class User(db.Model):   id = db.Column(db.Integer(), primary_key=True)   email = db.Column(db.String(100), unique=True)   password = db.Column(db.String(100))   date_updated = db.Column(db.DateTime())    def __init__(self, email, password, date_updated=None):     self.email = email     self.password = password     self.date_updated = datetime.utcnow() 

When I create a new User object, my date_updated field gets set to the current time. What I'd like to do is make it so that whenever I save changes to my User object my date_updated field is set to the current time automatically.

I've scoured the documentation, but for the life of me I can't seem to find any references to this. I'm very new to SQLAlchemy, so I really have no prior experience to draw from.

Would love some feedback, thank you.

Answer 1

Just add server_default or default argument to the column fields:

created_on = db.Column(db.DateTime, server_default=db.func.now()) updated_on = db.Column(db.DateTime, server_default=db.func.now(), server_onupdate=db.func.now()) 

I prefer the {created,updated}_on column names. ;)

SQLAlchemy docs about column insert/update defaults.

[Edit]: Updated code to use server_default arguments in the code.

[Edit 2]: Replaced onupdate with server_onupdate arguments.

Answer 2

date_created  = db.Column(db.DateTime,  default=db.func.current_timestamp()) date_modified = db.Column(db.DateTime,  default=db.func.current_timestamp(),                                        onupdate=db.func.current_timestamp())