Flask-Cors: solving cross-domain issues in Python web applications

Cross-domain issues are a very common problem when developing web applications. Due to the same-origin policy restrictions of the browser, the request must be issued under the current domain name, otherwise it will be restricted. This makes data interaction between servers under different domain names very difficult.

In order to solve this problem, a common way is to perform corresponding processing on the server side, that is, to set the corresponding cross-domain request response header. Flask-Cors is an excellent Python library for solving cross-domain problems.

What are Flask-Cors?

Flask-Cors is a member of the Flask extension library. Its main function is to provide Flask applications with the ability to easily resolve cross-domain requests. It allows Flask applications to support cross-domain requests and provides a simple and easy-to-use API for us to quickly configure and call in code.

How to use Flask-Cors?

Before using Flask-Cors, you need to install the Flask-Cors library through package management tools such as pip.

Next, to reference and configure Flask-Cors in the Flask application, you can use the following code:

from flask import Flask, jsonify
from flask_cors import CORS

app = Flask(__name__)

# 允许跨域请求
CORS(app, resources=r'/*')

# 路由
@app.route('/')
def index():
    return jsonify(message='Hello World!')

# 启动服务器
if __name__ == '__main__':
    app.run()

Create a new CORS application object using the CORS class, by passing in Flask Configure the application instance app and the list of resources that allow cross-domain requests. In the above example, we set up all resources to allow cross-origin requests.

In addition to the above code, Flask-Cors also provides other APIs for more flexibly configuring cross-domain request response headers.

For example, we can also use the CORS method that supports specific HTTP methods, as shown below:

from flask import Flask, jsonify
from flask_cors import CORS

app = Flask(__name__)

# 设置只支持GET、HEAD和OPTIONS方法的跨域请求
cors = CORS(app, resources={r'/api/*': {'origins': '*'}, 'methods': ['GET', 'HEAD', 'OPTIONS']})

# 路由
@app.route('/api/test', methods=['GET'])
def test():
    return jsonify(message='Success!')

# 启动服务器
if __name__ == '__main__':
    app.run()

Here, we specify all requests under the "/api/*" path, and Limited to cross-domain responses of the three methods GET, HEAD and OPTIONS.

Summary

Flask-Cors is a very excellent extension library for solving cross-domain requests in Python web applications. It not only provides cross-domain requests that support specific HTTP methods, but also has many flexible APIs for users to configure. Using Flask-Cors can greatly reduce the difficulty of developers' work in dealing with cross-domain issues and improve development efficiency.

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