SQLAlchemy ORM conversion to pandas DataFrame
Below should work in most cases: df = pd.read_sql(query.statement, query.session.bind) See pandas.read_sql documentation for more information on the parameters.
sqlalchemy
ImportError: No module named MySQLdb
If you’re having issues compiling the binary extension, or on a platform where you cant, you can try using the pure python PyMySQL bindings. Simply pip install pymysql and switch your SQLAlchemy URI to start like this: SQLALCHEMY_DATABASE_URI = ‘mysql+pymysql://…..’ There are some other drivers you could also try.
sqlalchemy flush() and get inserted id?
I’ve just run across the same problem, and after testing I have found that NONE of these answers are sufficient. Currently, or as of sqlalchemy .6+, there is a very simple solution (I don’t know if this exists in prior version, though I imagine it does): session.refresh() So, your code would look something like this: … Read more
sqlalchemy.exc.NoSuchModuleError: Can’t load plugin: sqlalchemy.dialects:postgres
The URI should start with postgresql:// instead of postgres://. SQLAlchemy used to accept both, but has removed support for the postgres name.
SQLAlchemy: cascade delete
The problem is that sqlalchemy considers Child as the parent, because that is where you defined your relationship (it doesn’t care that you called it “Child” of course). If you define the relationship on the Parent class instead, it will work: children = relationship(“Child”, cascade=”all,delete”, backref=”parent”) (note “Child” as a string: this is allowed when … Read more
sqlalchemy IS NOT NULL select
column_obj != None will produce a IS NOT NULL constraint: In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL. or use is_not()*: Implement the IS NOT operator. Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. … Read more
Flask-SQLalchemy update a row’s information
Retrieve an object using the tutorial shown in the Flask-SQLAlchemy documentation. Once you have the entity that you want to change, change the entity itself. Then, db.session.commit(). For example: admin = User.query.filter_by(username=”admin”).first() admin.email=”my_new_email@example.com” db.session.commit() user = User.query.get(5) user.name=”New Name” db.session.commit() Flask-SQLAlchemy is based on SQLAlchemy, so be sure to check out the SQLAlchemy Docs as … Read more
How do I know if I can disable SQLALCHEMY_TRACK_MODIFICATIONS?
Most likely your application doesn’t use the Flask-SQLAlchemy event system, so you’re probably safe to turn off. You’ll need to audit the code to verify–you’re looking for anything that hooks into models_committed or before_models_committed. If you do find that you’re using the Flask-SQLAlchemy event system, you probably should update the code to use SQLAlchemy’s built-in … Read more
Strange SQLAlchemy error message: TypeError: ‘dict’ object does not support indexing
You have to give %% to use it as % because % in python is use as string formatting so when you write single % its assume that you are going to replace some value with this. So when you want to place single % in string with query allways place double %.
Flask SQLAlchemy query, specify column names
You can use the with_entities() method to restrict which columns you’d like to return in the result. (documentation) result = SomeModel.query.with_entities(SomeModel.col1, SomeModel.col2) Depending on your requirements, you may also find deferreds useful. They allow you to return the full object but restrict the columns that come over the wire.