Can you explain the concept of the application lifecycle in FastAPI and how it is implemented?

The application lifecycle in FastAPI includes startup and shutdown phases, where initialization and cleanup of resources can be performed.

FastAPI implements this through startup and shutdown events. You can register functions that will be called when the application starts (e.g., connecting to a database) and when it shuts down (e.g., closing connections).

Example:

from fastapi import FastAPI

app = FastAPI()

@app.on_event("startup")
async def startup_event():
    print("Connecting to the database")
    # resource initialization

@app.on_event("shutdown")
async def shutdown_event():
    print("Closing connections")
    # resource cleanup

Thus, the lifecycle helps manage resources and perform necessary actions during application startup and shutdown.