FastAPI instead of built-in Fletd server. Mixed async/sync apps.

[FeodorFitsner]

• runtime is async by default, Flet is async-first framework.
• two types of backend: fast api, socket server
• diagram with event loop, pool threads.
• mix sync and async handlers.
• no need to use _async methods in the most cases.
• UserControl is deprecated.
• page.run_thread() and page.run_task() and page.executor and page.loop.
• Run with any ASGI web server:

app = ft.app(main, export_asgi_app=True)

Run with Hypercorn:

hypercorn path.to.your.main:app --bind 0.0.0.0:8000

API changes

• Replace import flet_fastapi with import flet.fastapi as flet_fastapi.
• ft.app(export_asgi_app). How assets, upload folders are resolved?
• Control.did_mount_async() and Control.will_unmount_async() are not called anymore. Use Control.did_mount() and Control.will_unmount() instead.
• Use .update() and .add() in both sync and async handlers.
• Control._before_build_command() replaced with Control.before_update().
• Control._is_isolated() replaced with Control.is_isolated().
• OAuth handler URL endpoint changed from /api/oauth/redirect to /oauth_callback. Use FLET_OAUTH_CALLBACK_HANDLER_ENDPOINT env var to customize.

Deprecated methods

• Audio.pause_async
• Audio.play_async
• Audio.release_async
• Audio.resume_async
• Audio.seek_async
• AudioRecorder.pause_recording_async
• AudioRecorder.resume_recording_async
• AudioRecorder.start_recording_async
• Canvas.clean_async
• Column.clean_async
• DatePicker.pick_date_async
• Dismissible.confirm_dismiss_async
• Dropdown.focus_async
• ElevatedButton.focus_async
• FilePicker.get_directory_path_async
• FilePicker.pick_files_async
• FilePicker.save_file_async
• FilePicker.upload_async
• GridView.clean_async
• HapticFeedback.heavy_impact_async
• HapticFeedback.light_impact_async
• HapticFeedback.medium_impact_async
• HapticFeedback.vibrate_async
• IconButton.focus_async
• ListView.clean_async
• MenuItemButton.focus_async
• OutlinedButton.focus_async
• Page.add_async
• Page.clean_async
• Page.close_banner_async
• Page.close_bottom_sheet_async
• Page.close_dialog_async
• Page.close_drawer_async
• Page.close_end_drawer_async
• Page.close_in_app_web_view_async
• Page.error_async
• Page.get_upload_url_async
• Page.go_async
• Page.insert_async
• Page.launch_url_async
• Page.logout_async
• Page.remove_async
• Page.remove_at_async
• Page.scroll_to_async
• Page.set_clipboard_async
• Page.show_banner_async
• Page.show_bottom_sheet_async
• Page.show_dialog_async
• Page.show_drawer_async
• Page.show_end_drawer_async
• Page.show_snack_bar_async
• Page.update_async
• Page.window_center_async
• Page.window_close_async
• Page.window_destroy_async
• Page.window_to_front_async
• Pagelet.close_drawer_async
• Pagelet.close_end_drawer_async
• Pagelet.show_drawer_async
• Pagelet.show_end_drawer_async
• PubSub.send_all_async
• PubSub.send_all_on_topic_async
• PubSub.send_others_async
• PubSub.send_others_on_topic_async
• PubSub.subscribe_async
• PubSub.subscribe_topic_async
• PubSub.unsubscribe_all_async
• PubSub.unsubscribe_async
• PubSub.unsubscribe_topic_async
• ResponsiveRow.clean_async
• Row.clean_async
• ScrollableControl.scroll_to_async
• SearchBar.close_view_async
• SearchBar.open_view_async
• SubmenuButton.focus_async
• TextButton.focus_async
• TextField.focus_async
• TimePicker.pick_time_async
• Video.next_async
• Video.pause_async
• Video.play_async
• Video.play_or_pause_async
• Video.playlist_add_async
• Video.playlist_remove_async
• Video.previous_async
• Video.stop_async

Environment variables

• FLET_FORCE_WEB_SERVER
• FLET_SERVER_PORT - 8000 is program is run on a Linux server or FLET_FORCE_WEB_SERVER is set; otherwise random port.
• FLET_SERVER_IP, bounds to all server IPs by default.
• FLET_ASSETS_DIR
• FLET_UPLOAD_DIR
• FLET_MAX_UPLOAD_SIZE, bytes. Unlimited if not specified.
• FLET_SECRET_KEY - for uploads
• FLET_WEB_APP_PATH
• FLET_SESSION_TIMEOUT, seconds. Default is 3600.
• FLET_OAUTH_STATE_TIMEOUT, seconds. Default is 600.
• FLET_WEB_RENDERER - canvaskit (default), html or auto.
• FLET_WEB_USE_COLOR_EMOJI. true, or True or 1.
• FLET_WEB_ROUTE_URL_STRATEGY - path (default) or hash.
• FLET_WEBSOCKET_HANDLER_ENDPOINT - default /ws.
• FLET_UPLOAD_HANDLER_ENDPOINT - default /upload.
• FLET_OAUTH_CALLBACK_HANDLER_ENDPOINT - default /oauth_callback.

Sync countdown example

import time

import flet as ft


class Countdown(ft.UserControl):
    def __init__(self, seconds):
        super().__init__()
        self.seconds = seconds

    def did_mount(self):
        self.running = True
        self.page.run_in_thread(self.update_timer)

    def will_unmount(self):
        self.running = False

    def update_timer(self):
        while self.seconds and self.running:
            mins, secs = divmod(self.seconds, 60)
            self.countdown.value = "{:02d}:{:02d}".format(mins, secs)
            self.update()
            time.sleep(1)
            self.seconds -= 1

    def build(self):
        self.countdown = ft.Text()
        return self.countdown


def main(page: ft.Page):
    page.add(Countdown(120), Countdown(60))


ft.app(main)

Async countdown example

import asyncio

import flet as ft


class Countdown(ft.UserControl):
    def __init__(self, seconds):
        super().__init__()
        self.seconds = seconds

    def did_mount(self):
        self.running = True
        self.page.run_task(self.update_timer)

    def will_unmount(self):
        self.running = False

    async def update_timer(self):
        while self.seconds and self.running:
            mins, secs = divmod(self.seconds, 60)
            self.countdown.value = "{:02d}:{:02d}".format(mins, secs)
            self.update()
            await asyncio.sleep(1)
            self.seconds -= 1

    def build(self):
        self.countdown = ft.Text()
        return self.countdown


def main(page: ft.Page):
    page.add(Countdown(120), Countdown(60))


ft.app(main)