CODEWITHSUNDEEP
pythondatabasepython-3.xsqlalchemy
Logicman
Logicman

Reputation: 129

Creating a database with SQLAlchemy once without recreating it every time the program runs

My program is built to buy and sell (fake) shares of a stock, then add each transaction to a database. I'm using SQLAlchemy to create the database and tables, and so far it works great. There is one rather large issue though: Since I create the tables within my program (and my program is constantly looping), every time it loops the tables are recreated.

Tables:

class Wallet(Base):
    __tablename__ = 'wallets'

    id = Column(Integer, Sequence('wallet_id_seq'), primary_key=True)
    name = Column(String(50))
    balance = Column(Integer())

    def __repr__(self):
        return "<Wallet(name='%s', balance='%s')>" % (self.name, self.balance)

class Transaction(Base):
    __tablename__ = 'transactions'

    id = Column(Integer, Sequence('transaction_id_seq'), primary_key=True)
    stock = Column(String(50))
    symbol = Column(String(50))
    buy_or_sell = Column(String(50))
    price = Column(Integer())
    ema = Column(Integer())
    shares = Column(Integer())
    time = Column(String(50))

    def __repr__(self):
        return "<Transaction(stock='%s', symbol='%s', buy_or_sell='%s', price='%s', ema='%s', shares='%s', time='%s')>" % (self.stock, self.symbol, self.buy_or_sell, self.price, self.ema, self.shares, self.time)

I tried to relocate the tables to another Python file and import them so I could loop the main program over and over without recreating them.

bin/
    main.py
    databases.py
    __init__.py

But the issue is persisting. I'm guessing it's because every time classes Wallet and Transaction are imported it recreates the tables. Or maybe it's just that the database create_all function (Base.metadata.create_all(engine)) is still in main.py and runs on every loop.

How do I create the database once and then update its rows/columns every time main.py runs?

Upvotes: 0

Views: 734

Answers (1)

Logicman
Logicman

Reputation: 129

Credit to Jonas for answering my question. By creating the database in temporary memory it was being deleted every loop. The solution is using an actual file instead.

Upvotes: 1

Related Questions