First acquaintance with Flask

Flask Framework Components

Flask_sqlalchemy: A good combination of Flask and SQLAlchemy, such as ORM operations in django
flask_script: used to generate commands, use commands in the project root directory path; for example: python manage.py runserver
flask_migrate: used to implement database migration (depending on flask_script)
flask-session: session is placed in redis
blinker: signal - trigger signal. Mainly to allow developers to customize some behaviors during the flask request process

Briefly describe the Flask context management process

There are two contexts in Flask, **request context** and **application context**.

1. Request context: saves the data that the client and server interact with.

Application context: some configuration information saved during the running process of the flask program, such as program file name, database connection, user information, etc.

request and session belong to the request context object.

request: Encapsulates the content of the HTTP request, which is for the HTTP request.Example: user = request.args.get('user'), which gets the parameters of the get request.

Session: used to record the information in the request session, for user information.For example: session['name'] = user.id, user information can be recorded.You can also get user information through session.get('name')

current_app and g both belong to the application context object.

current_app: Indicates the program instance of the currently running program file.

g: The object used for temporary storage when processing requests, this variable will be reset for each request.For example: we can obtain some user information for temporary requests.

When calling app = Flask(_name_), the program application object app is created;
request When every http request occurs, the WSGI server calls Flask.call(); then the request object created inside Flask;
The life cycle of the app is longer than request and g. During the life of an app, multiple http requests may occur, so there will be multiple requests and g.
Finally, the view function is passed in, and the response object is generated by return, redirect or render_template and returned to the client.