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8 months ago Flask-Cors
How to Install Flask-CORS in Python
In this article, we will learn to install Flask-CORS which is a Python module and a Flask extension that supports and allows cross-origin resource sharing (CORS) through a simple decorator. Due to security concerns, cross-domain cookie submission is disabled by default. We will look at how to install Flask-Cors on the Linux operating system.
What is Python CORS?
When one domain requests a resource from another domain, this is referred to as cross-origin resource sharing or CORS. When a front-end and back-end are in distinct origins, this happens most commonly. Using JavaScript scripts, which share similar principles with the backend, the frontend communicates with the backend. Cross-origin AJAX is made possible with Flask CORS, which is only the Flask plugin for managing CORS.
What are Flask-Cors used for?
It enables communication with resources housed in many domains. It’s a crucial protocol for enabling cross-domain queries when there is a justifiable need to do so. Install the Flask-Cors package Step 1: Run the below command in the terminal to install Python3 on your Linux OS:
sudo apt-get install python3
Step 2: Next, install the pip module, which is required for Python3 package installation and management. As a result, use the below command:
sudo apt install python3-pip
Step 3: Once the installation is complete, verify it by looking at the Python and pip versions:
python3 --version
pip --version The version number may differ, but it will look like this:
Step 4: Use the below command to install the Flask-Cors package:
pip install Flask-Cors
Step 5: Run the below command in the terminal to see if the Flask-Cors package has been successfully installed on your Linux Machine:
python3 -m pip show Flask-Cors
If the installation is successful, the following information would be visible on the terminal screen:
How to Enable CORS in the Flask
Method 1: To enable CORS for all domains on all routes, initialize the Flask-Cors extension with default parameters.
from flask import Flask
from flask_cors import CORS
app = Flask(__name__)
CORS(app)
@app.route("/")
def welcome():
return "Hello world! Welcome by Kushal"
Method 2: Simply add @cross_origin() below a call route to Flask’s @app. route(..) to allow CORS on a given route.
@app.route("/")
@cross_origin()
def helloWorld():
return "Hello world! Welcome by Kushal"Usage of Flask-Cors Package
This package exposes a Flask extension that enables CORS support by default on all routes, origins, and methods and provides a simple decorator for decorating Flask routes. To accept the default options and allow CORS on a given route, @cross origin() is to be added after a call to Flask’s @app.route(). Refer to the following function with different options to learn further about it.
flask_cors.cross_origin(
origins = '*',
methods = ['GET', 'HEAD', 'POST', 'OPTIONS', 'PUT'],
headers = None,
supports_credentials = False,
max_age = None,
send_wildcard = True,
always_send = True,
automatic_options = False
)
Flask-Cors
Flask-Cors is a Flask extension that provides Cross-Origin Resource Sharing (CORS) support for Flask applications. It enables developers to configure Cross-Origin HTTP requests in their Flask applications, allowing web applications hosted on different domains to communicate with each other securely. Here's an overview of Flask-Cors:
Features:
Cross-Origin Resource Sharing (CORS) Support: Flask-Cors enables Cross-Origin HTTP requests in Flask applications by adding the necessary CORS headers to HTTP responses. It allows web browsers to make requests to a domain different from the one that served the original web page, thus enabling cross-origin communication.
Flexible Configuration Options: Flask-Cors provides a range of configuration options for fine-tuning CORS behavior in Flask applications. Developers can specify allowed origins, methods, headers, and other CORS-related settings to control which cross-origin requests are allowed and how they are handled.
Decorator-Based Usage: Flask-Cors allows developers to apply CORS settings to specific routes or views using simple decorators. By decorating Flask route functions with
@cross_origin, developers can enable CORS support for those routes and specify CORS options directly in the decorator.Global Configuration: In addition to route-specific configuration, Flask-Cors supports global configuration settings that apply to all routes in the application. Developers can set default CORS options in the Flask application configuration or using environment variables to ensure consistent CORS behavior across all routes.
Preflight Requests Handling: Flask-Cors automatically handles preflight requests (OPTIONS requests) by responding with appropriate CORS headers and handling CORS preflight checks. This simplifies the process of handling complex cross-origin requests and ensures compliance with CORS specifications.
Integration with Flask Extensions: Flask-Cors integrates seamlessly with other Flask extensions and features, including Flask-RESTful, Flask-Security, and Flask-JWT-Extended. It provides utilities for configuring CORS settings for RESTful APIs, authentication endpoints, and other parts of the Flask application.
Security Considerations: Flask-Cors includes security features to protect against Cross-Site Request Forgery (CSRF) attacks and other security vulnerabilities associated with cross-origin requests. It provides options for specifying allowed origins, methods, and headers to prevent unauthorized access and protect sensitive data.
Advantages:
Cross-Domain Communication: Flask-Cors enables secure cross-origin communication between web applications hosted on different domains, allowing developers to build interactive and collaborative web applications that integrate with third-party services and APIs.
Fine-Grained Control: Flask-Cors provides fine-grained control over CORS settings, allowing developers to specify allowed origins, methods, headers, and other CORS-related options at both the route and global levels. This flexibility enables developers to customize CORS behavior to suit their application's requirements.
Simplified Configuration: Flask-Cors simplifies the process of configuring CORS support in Flask applications by providing easy-to-use decorators and configuration options. Developers can enable CORS support with just a few lines of code, reducing the complexity of handling cross-origin requests.
Security: Flask-Cors includes security features to protect against common security vulnerabilities associated with cross-origin requests, such as CSRF attacks and unauthorized access to sensitive data. By specifying allowed origins, methods, and headers, developers can prevent malicious cross-origin requests and ensure the security of their applications.
Conclusion:
Flask-Cors is a valuable tool for enabling Cross-Origin Resource Sharing (CORS) support in Flask applications. It simplifies the process of configuring CORS settings and provides fine-grained control over cross-origin requests, allowing developers to build secure and interactive web applications that communicate with third-party services and APIs. Whether you're building a single-page application, a RESTful API, or a web-based dashboard, Flask-Cors offers the features and flexibility you need to handle cross-origin requests effectively and securely.