Formatting the Datetime string with SQLAlchemy

Question

Can I just say first of all I've been really enjoying the SQLAlchwemy and Flash content, and I've made a little website with it. and plan to do a bigger one in time.

I'm almost ready to deploy it somewhere, but there's just one little thing.

I'd like to be able to display a string format for the Datetime object that is used for one of my fields.

Here's the model I'm using.

 # Declare imports for the app
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import datetime


# Connect to SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///roster.db'

app.secret_key = "[SECRET KEY GOES HERE]"  # Secret key


db = SQLAlchemy(app)


# Create Database Model - 3 fields + ID as primary key
class Roster(db.Model):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column("Name", db.String(80), unique=True, nullable=False)
    age = db.Column("Age", db.Integer, unique=True, nullable=False)
    joined = db.Column('Joined', db.DateTime, default=datetime.datetime.now)

    def __repr__(self):
        return f'''<Roster %r> ({self.name} 
        Age: {self.age}
        Joined: {self.joined }
       '''

which returns a string like 2021-09-09 15:44:15.817857 for that column. Is there a way to do this? The obvious answer would seem to me to be to use `strftime() instead rather than datetime.now but SQLAlchemy doesn't seem to support it.

Is there not a way to format it to something more readable? Thanks. :)

Answer 1 · 2021-09-09T18:04:20Z

September 9, 2021 6:04pm

I don't know if you can specify the format of the datetime directly in SQLAlchemy.

You could create a method inside your Roster class to return the formatted datetime, and call that method instead of accessing joined from outside the class.

You could change joined into a db.String column and convert the datetime to a string of the correct format before storing in the model. This could lose some precision depending on the format of the string, since it would no longer be a datetime object. It would also require passing arguments to the strftime function without calling the function immediately. One way to do that would be to create a function outside the Roster class with no parameters that returns the string, and pass the reference to that function as the default value for joined.

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Jonathan Grieve

Jonathan Grieve

Formatting the Datetime string with SQLAlchemy

1 Answer

jb30

jb30

Jonathan Grieve

Jonathan Grieve