Skip to content

Instantly share code, notes, and snippets.

@kovalbogdan95

kovalbogdan95/singleton.py

Created August 20, 2020 16:06
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save kovalbogdan95/73561ffb625915bbe6fa0465cb7f6bc3 to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save kovalbogdan95/73561ffb625915bbe6fa0465cb7f6bc3 to your computer and use it in GitHub Desktop.
Download ZIP

Revisions

  1. kovalbogdan95 created this gist Aug 20, 2020.
    37 changes: 37 additions & 0 deletions singleton.py
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,37 @@
    from sqlalchemy.orm.exc import NoResultFound
    from sqlalchemy.exc import IntegrityError
    from rates.extensions import db


    class LoadSingleton:
    @classmethod
    def load(cls):
    id_ = {"id": 1}
    try:
    return db.session.query(cls).filter_by(**id_).one()
    except NoResultFound:
    try:
    with db.session.begin_nested():
    instance = cls(**id_)
    db.session.add(instance)
    db.session.commit()
    return instance
    except IntegrityError:
    return db.session.query(cls).filter_by(**id_).one()


    class Rate(db.Model, LoadSingleton):
    """
    Model to store rate value
    """

    __tablename__ = "rate"

    id = db.Column(db.Integer, primary_key=True)
    value = db.Column(db.Float, nullable=False, default=500)

    def __repr__(self):
    return f"<Rate value:{self.value}>"

    # Usage
    rate = Rate().load().value