fast-start.py

print("__name__ is", __name__)
DEV = True # True for development with hot reload, False for production with no hot reload

from nicegui.ui_run import run as ui_run # just importing the function to run the server

if not DEV or not __name__ == "__main__": # you can do `if True:` to bypass this to revert to the normal behavior, but that is slow...
    # Explanation: 2 reasons for running this code:
    # 1. not in dev mode, so there is no __mp_main__, this is already where NiceGUI will run
    # 2. or, in dev mode, and this is the __mp_main__, so we want to run this code
    
    print("Here are a bunch of startup tasks that must be run once, and before the server starts")
    for _ in range(100000000):
        pass # some long running task
    print("Before-server-start startup tasks are done")

    from nicegui import ui, app # the normal import

    @ui.page("/")
    def index():
        print("Here are some tasks you want to run before every page load")
        ui.label("You page definitions go here")

    def delayed_startup_tasks():
        print("Here are a bunch of startup tasks that also must be run once, but can be after the server has started")
        for _ in range(100000000):
            pass # some long running task
        print("After-server-start startup tasks are done")
    app.on_startup(delayed_startup_tasks)
    

ui_run(reload=DEV) # DEV mode will reload the server when the code changes

# This means: 
# If it is DEV mode, __main__ simply runs ui_run, which will start the server, spawn __mp_main__ and run the code above to start the server
# If it is not DEV mode, __main__ will run the code above, and then run ui_run, which will start the server directly