Pip install flask sqlalchemy with code examples
Flask is a popular micro web framework for building web applications in Python. SQLAlchemy is a SQL toolkit and Object-Relational Mapping (ORM) library for Python. By integrating Flask with SQLAlchemy, developers can easily connect their Flask applications to a database and start working with it. In this article, we will go through the process of installing Flask and SQLAlchemy, and demonstrate how to use them together with code examples.
Installing Flask and SQLAlchemy
The first step in using Flask and SQLAlchemy together is to install them. Flask can be installed using pip, the Python package manager, by running the following command in the terminal:
pip install flask
SQLAlchemy can be installed in a similar manner:
pip install sqlalchemy
Once both Flask and SQLAlchemy are installed, we can start using them in our application.
Creating a Flask application
Before we start integrating Flask and SQLAlchemy, let's create a basic Flask application. To do this, create a new file named app.py and add the following code:
from flask import Flask
app = Flask(__name__)
@app.route("/")
def home():
return "Hello, World!"
if __name__ == "__main__":
app.run(debug=True)
This code creates a new Flask application and sets up a single route, "/", that returns the message "Hello, World!". The if __name__ == "__main__" block at the end of the code makes sure that the application runs only if the file is executed as the main program, and not if it is imported as a module.
To run the application, simply execute the app.py file in the terminal:
python app.py
If everything is set up correctly, you should see the following output:
* Debugger is active!
* Debugger PIN: 123-456-789
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
This means that the application is running and can be accessed at http://127.0.0.1:5000/ in a web browser.
Integrating Flask and SQLAlchemy
Now that we have a basic Flask application set up, let's integrate it with SQLAlchemy. To do this, we need to add the following code to our app.py file:
from flask_sqlalchemy import SQLAlchemy
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
db = SQLAlchemy(app)
This code imports the SQLAlchemy class from the flask_sqlalchemy module and sets the database URI for the application. The database URI is used to specify the type of database we are connecting to and its location. In this case, we are using an SQLite database located at test.db.
Defining a model
The next step is to define a model for our database. A model is a Python class that represents a table in the database. To define a model, we need to create a new file named models.py and add the following code to it:
“
from app import db
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True, nullable=False)
email = db.Column(db.String(120), unique=True, nullable=False)
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## Popular questions
1. What is Flask?
Answer: Flask is a micro web framework for building web applications in Python. It is a lightweight framework that provides a simple and easy-to-use interface for building web applications.
2. What is SQLAlchemy?
Answer: SQLAlchemy is a SQL toolkit and Object-Relational Mapping (ORM) library for Python. It provides a set of high-level API’s for connecting to relational databases and performing common database operations, such as creating tables, inserting data, and querying data.
3. How can I install Flask and SQLAlchemy?
Answer: Flask and SQLAlchemy can be installed using the Python package manager pip. To install Flask, run the following command in the terminal: `pip install flask`. To install SQLAlchemy, run the following command: `pip install sqlalchemy`.
4. How can I integrate Flask and SQLAlchemy in a Flask application?
Answer: To integrate Flask and SQLAlchemy in a Flask application, you need to import the `SQLAlchemy` class from the `flask_sqlalchemy` module, set the database URI for the application, and create a new instance of the `SQLAlchemy` class. The database URI is used to specify the type of database you are connecting to and its location.
5. What is a model in SQLAlchemy?
Answer: A model in SQLAlchemy is a Python class that represents a table in the database. A model class is defined using the `db.Model` base class and defines columns for the table using `db.Column` instances. Each column represents a field in the table and is defined with its type and properties, such as whether it is a primary key or whether it allows null values.
### Tag
Web Development
