Flask update query

Question

In my Flask web app I have a login system. When user logged, in the table of my database I want to update the datetime when user made the last login. I'm using this code:

 @app.route('/login', methods=['POST'])
 def do_admin_login():
     POST_CODICE_FISCALE = str(request.form['codice_fiscale'])
     POST_PASSWORD = str(request.form['password'])
     pwd_enc=base64.b64encode(POST_PASSWORD)

     Session = sessionmaker(bind=engine)
     s = Session()
     query = s.query(User).filter(User.codice_fiscale.in_([POST_CODICE_FISCALE]), User.password.in_([pwd_enc]))
     result = query.first()
     if result:
        session['logged_in'] = True
        query = s.query(User).filter(User.codice_fiscale.in_([POST_CODICE_FISCALE]).update(User.data_ora_ultimo_accesso=datetime.now()))  
        query.first()
        db.session.commit()
    else:
        flash('wrong password!')
    return home()

but I receive the error:

 query = s.query(User).filter(User.codice_fiscale.in_([POST_CODICE_FISCALE]).update(User.
 data_ora_ultimo_accesso=datetime.now())) 
 SyntaxError: keyword can't be an expression

what it is wrong? thanks.

Ilja Everilä · Accepted Answer · 2017-06-01 14:06:06Z

1

As the error says, a keyword in a function call argument list cannot be an expression, such as User.data_ora_ultimo_accesso, but an identifier. Instead you should pass Query.update() a dictionary of column, expression pairs:

    query = s.query(User).\
        filter(User.codice_fiscale.in_([POST_CODICE_FISCALE]).\
        update({ User.data_ora_ultimo_accesso: datetime.now() },
               synchronize_session=False))

Note that since you commit right away, there's no need to synchronize the session, since all state will be expired anyway.

You could also make some changes that'd improve your code's readability. For example instead of

filter(User.codice_fiscale.in_([POST_CODICE_FISCALE]),
       User.password.in_([pwd_enc]))

just

filter(User.codice_fiscale == POST_CODICE_FISCALE,
       User.password == pwd_enc)

No point in checking if a list of 1 item contains something, compared to just testing equality.

Finally, you create a new Session class and an instance s of it, but you commit a different session: db.session, which you should've probably been using all along. What this means is that your updates will not take place, as that session's transaction is not actually committed.

edited Jun 1, 2017 at 14:06

answered Jun 1, 2017 at 13:33

Ilja Everilä

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4 Comments

Giuseppe Ricci Over a year ago

Thanks. it works without errors but it seems in database data_ora_ultimo_accesso isn't update.

Ilja Everilä Over a year ago

Did you fix your session handling? Don't create separate session, but use the db.session consistently. Btw you could also use the ORM to perform the update: result.codice_fiscale = datetime.now() and then commit.

Giuseppe Ricci Over a year ago

Do you mean to use the same session: Session = sessionmaker(bind=engine) s = Session() How can I use db.session consistently?

Ilja Everilä Over a year ago

In other words don't create sessions, but use the one provided to you by flask-sqlalchemy: db.session.

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