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How to use flask sqlalchemy function

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by aryaman@openweaver.com dot icon Updated: Oct 19, 2023

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Flask's abort() is a unique tool for web developers. It helps them handle unexpected issues on their websites.


Think of it like having tools in your car for unexpected problems like a flat tire. Flask's abort() is a web developer's tool to deal with unforeseen website issues.  

 

It can manage issues like saying, "Oops, we can't find this page," or "Uh-oh, something went wrong." Developers can choose the message for these problems.  

 

Using Flask's abort() is essential. If not, it could create problems like using the wrong tool. A great thing about Flask's abort() is that it prevents big website crashes. It stops things from breaking and shows a helpful error message to visitors.  

 

Flask's abort() function is a valuable tool for web developers to manage website issues. Developers must know what the device can do and improve user error messages. If things go wrong, tools like the pdb debugger or Flask's web debug toolbar can help discover why.  

CODE

Proper sqlalchemy use in flask

PythondotLines of Code : 37dotLicense : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries : 
import flask
import sqlalchemy
from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class Item (Base):

    __tablename__ = 'items'

    id = Column(Integer, primary_key=True)
    title = Column(String)    

engine = sqlalchemy.create_engine('sqlite:///bestappever.db', echo=True)
Session = sessionmaker(bind=engine)

# create all tables if you wish...
Base.metadata.create_all(engine)

app = flask.Flask(__name__)

@app.before_request
def create_session():
    flask.g.session = Session()

@app.teardown_appcontext
def shutdown_session(response_or_exc):
    flask.g.session.commit()
    flask.g.session.remove()

@app.route('/')
    # just use the SQLAlchemy session :)
    items = flask.g.session.query(Item).all()
    return flask.render_template('index.html', items=items)
  1. Copy the code using the "Copy" button above, and paste it into a Python file in your IDE.
  2. Install flask and sqlalchemy using the pip command.
  3. Add a function definition in the @app.route('\') as `def index():` in place of the comment line.
  4. Run the file to check the output.


I hope you found this helpful. I have added the link to dependent libraries and version information in the following sections.

Dependent Libraries

flaskby pallets

Python doticonstar image 63300 doticonVersion:2.2.5doticon
License: Permissive (BSD-3-Clause)

The Python micro framework for building web applications.

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            flaskby pallets

            Python doticon star image 63300 doticonVersion:2.2.5doticon License: Permissive (BSD-3-Clause)

            The Python micro framework for building web applications.
            Support
              Quality
                Security
                  License
                    Reuse

                      Environment Tested

                      I tested this solution in the following versions. Be mindful of changes when working with other versions.

                      1. The solution is created in Python-3.11.
                      2. The solution is created in SQLAlchemy-2.0.21

                      FAQ

                      1. How does Flask SQLAlchemy provide database access?  

                      Flask-SQLAlchemy provides database access in Flask applications by integrating SQLAlchemy. It is a powerful and flexible Object-Relational Mapping (ORM) library in Flask. It simplifies database interactions by offering a Flask extension. This manages database connections, sessions, and models. With Flask-SQLAlchemy, developers can define database models as Python classes. They can also interact with the database using familiar Python syntax. Thus making database access more straightforward and efficient.  

                       

                      2. What features make Python SQL more compatible with Flask than other languages?  

                      Python SQL is highly compatible with Flask due to several factors. First, both Flask and SQLAlchemy are written in Python. This allows them to seamlessly integrate with one another. Additionally, Python's simplicity and readability make it a preferred language for web development. Thus aligning well with Flask's philosophy of keeping things simple and minimalistic. Furthermore, Python's rich ecosystem, including NumPy, Pandas, Matplotlib, etc., complements Flask's capabilities. This allows developers to perform data processing and visualization tasks alongside web development.  

                       

                      3. What is flask dB, and how is it used in conjunction with SQLAlchemy?  

                      'Flask dB' refers to the Flask-Migrate extension, which SQLAlchemy uses for database migrations. Database migrations are essential for managing changes to database schemas. It also ensures that database structures stay synchronized with application code. Flask-Migrate offers a CLI for creating and applying migration scripts to the database. Developers can change and update database schema with the application's data models. This is done by running commands like 'flask dB migrate -m "description"' and 'flask dB upgrade,' 

                       

                      4. How do I import SQLAlchemy into my web applications?  

                      To import SQLAlchemy into your web applications, install the 'SQLAlchemy' package. Carry this out using a package manager like 'pip.' To use SQLAlchemy within your Flask application, include the following import statement: 

                      ```  

                      from sqlalchemy import SQLAlchemy  

                      ```  

                      Now, create and configure a SQLAlchemy object to work with your Flask application.  

                       

                      5. What are the steps to setting up a small web application with Flask and Sqlalchemy?  

                      Setting up a small web application with Flask and SQLAlchemy involves several steps:  

                        a. Install Flask and SQLAlchemy using 'pip.'  

                        b. Create a Flask application instance.  

                        c. Configure the application to connect to a database, specifying the database URI.  

                        d. Define database models as Python classes using SQLAlchemy's declarative syntax.  

                        e. Create and apply database migrations using Flask-Migrate if necessary.  

                        f. Define routes and views for your web application.  

                        g. Run the development server to test and debug your application.  


                      6. How do I create a new SQLite database file for use with Flask and Sqlalchemy?  

                      To create a new SQLite database file for use with Flask and SQLAlchemy, you can follow these steps:  

                        a. Import SQLAlchemy and create an instance of it in your Flask application.  

                        b. Configure the database URI in your Flask application. Also, specify the SQLite database file path.  

                        c. Define database models as Python classes, inheriting from SQLAlchemy's 'db. Model class.  

                        d. Run the Flask-Migrate command 'flask db init' to initialize migrations. And run 'flask dB migrate' to generate an initial migration script.  

                        e. Apply the migration with 'flask db upgrade'. This creates the SQLite database file and schema based on your defined models.  

                      These steps set up a new SQLite database file and allow you to use it with your Flask and SQLAlchemy applications.

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