flask:tldr:8dfb5

The command "flask run" is used to start a Flask application.

Flask is a web framework that allows developers to build web applications in Python. When you run the "flask run" command, it starts the development server, which will listen for incoming HTTP requests and serve the Flask application.

Here's how it works:

1. First, make sure you are in the root directory of your Flask application. The "flask run" command should be executed from within the application's directory.

2. When you run "flask run", Flask will automatically discover your application based on certain conventions. It will look for an application object (usually called "app") in a file named "app.py" or "wsgi.py" in the root directory.

3. Once the application is discovered, Flask will start the development server on the default host and port (typically "localhost:5000").

4. The development server will now listen for incoming HTTP requests. If a request is received, it will be routed to the appropriate Flask view function based on the URL and HTTP method.

5. The Flask application will then handle the request and return a response to the client.

Overall, the "flask run" command is a convenient way to quickly start a Flask application during development. It eliminates the need for manually configuring a web server and simplifies the process of running and testing the application.