Native modules¶

Native modules are PythonNative's wrappers around device APIs that aren't part of the view tree: the camera, GPS, file I/O, clipboard, share sheet, deep links, permissions, connectivity, secure storage, battery, haptics, biometrics, and the device-environment set React Native core ships (Keyboard, Dimensions, PixelRatio, Device, Localization, AccessibilityInfo). Each module is a Swift class in PythonNativeKit and a Kotlin class in the pythonnative Gradle module, registered by name; the Python class you call is a thin facade that routes through the native bridge. Off device (pn preview, pytest), the same facade resolves to a Python implementation with safe defaults (in-memory buffers, "unknown" states, no-op feedback), so app code stays single-source.

Every facade follows the same two rules, so you never need to look one up:

Sync or async is decided by what the OS has to do. A method is a plain function when the answer is already on the device and returns on the calling thread: Clipboard, Linking, Haptics / Vibration, Battery, NetInfo.fetch, SecureStore, AppState, FileSystem, Biometrics.is_available, Keyboard, Dimensions, PixelRatio, Device.info, Localization, and AccessibilityInfo. It is a coroutine when the OS has to prompt the user, drive hardware, or hand off to another process: Camera.take_photo / pick_from_gallery, Location.get_current, Share.share, Permissions.check / request, Biometrics.authenticate, Notifications.*, Alert.confirm / choose, and all of AsyncStorage. Inside a component, drive coroutines with an async def use_effect callback, use_resource, use_query, or pn.run_async(coro) from a sync handler.
Failures raise; "nothing happened" returns a value. A native error (a rejected call, a missing module, a bad argument) is a NativeModuleError and propagates like any other exception; FileSystem raises the standard OSError family. Outcomes that are not errors, such as the user cancelling a picker (None), dismissing the share sheet (False), or denying a permission ("blocked"), come back as values and are documented per method. No facade turns an exception into a default. Off device the desktop implementations never raise; they answer with the "nothing happened" value.

Several modules also ship reactive hooks: use_app_state, use_net_info, use_locales, use_screen_reader_enabled, and use_reduce_motion. Return values are frozen dataclasses (DeviceInfo, Locale, KeyboardEvent, DimensionsEvent, AccessibilityEvent) rather than dicts.

Permissions: declare them once, request at runtime¶

Declare the capabilities your app uses in the [permissions] table of pythonnative.toml. pn writes the matching Info.plist usage strings, AndroidManifest.xml <uses-permission> entries, background modes, and entitlements into the native projects for you (the full catalog is in the configuration reference):

[permissions]
camera = "So you can take photos in MyApp."
location_when_in_use = "So MyApp can show nearby content."
photo_library = "So you can pick photos from your library."
notifications = true

The strings appear in the system permission dialog on iOS, so write them as you would want a user to read them. The same keys are the names you pass to Permissions at runtime, so there is one vocabulary to learn.

Camera¶

Camera wraps photo capture and gallery picking. Both coroutines resolve to a path to the saved file (or None if the user cancelled).

import pythonnative as pn


@pn.component
def CameraScreen() -> pn.Node:
    photo, set_photo = pn.use_state("")

    async def take():
        path = await pn.Camera.take_photo()
        if path:
            set_photo(path)

    return pn.Column(
        pn.Button("Take photo", on_press=lambda: pn.run_async(take())),
        pn.Image(source=photo) if photo else pn.Spacer(),
    )

Cold-start permissions

The first call shows the system permission prompt. If the user denies it, subsequent calls resolve to None immediately; surface a helpful message in your UI rather than calling in a loop.

On Android, take_photo writes the full-resolution capture to a FileProvider URI handed to the camera app as EXTRA_OUTPUT, so the returned path is the real photo, not the intent's thumbnail. The library manifest declares the provider; allow_editing=True raises NativeModuleError("unsupported") on Android.

Location¶

Location.get_current reads a single GPS fix.

import pythonnative as pn


@pn.component
def WhereAmI() -> pn.Node:
    q = pn.use_query(pn.Location.get_current, [])
    if q.loading:
        return pn.Text("Acquiring location...")
    if q.data is None:
        return pn.Text("Location unavailable")
    lat, lon = q.data
    return pn.Text(f"{lat:.4f}, {lon:.4f}")

use_query manages the loading/data/error state for you and exposes a refetch() callable. get_current requests when-in-use permission inline on both platforms the first time it runs; a denial comes back as None.

For continuous updates, write a small native module that subscribes to CLLocationManagerDelegate (iOS) or LocationManager.requestUpdates (Android). Send updates through the module event channel; the Python callback can call set_state on the application thread.

File system¶

FileSystem answers the one question the standard library can't, "where may this app write?", and then gets out of the way. app_dir() is the app's sandboxed documents directory; path("notes/today.txt") resolves a relative name inside it and returns a pathlib.Path you use like any other. The read/write helpers are thin conveniences over that path and raise the same OSError subclasses open does (FileNotFoundError, PermissionError, ...). Everything is synchronous, exactly like the standard library it wraps; for large files, offload to a worker thread:

import asyncio
import pythonnative as pn

# Sync: fine for small files (preferences, JSON state, etc.)
pn.FileSystem.write_text("notes.txt", "hello")
text = pn.FileSystem.read_text("notes.txt")

# Work with the Path directly when you need more than the helpers.
for entry in sorted(pn.FileSystem.path("notes").iterdir()):
    print(entry.name)

# Async: explicitly offload to a worker thread for big payloads.
text = await asyncio.to_thread(pn.FileSystem.read_text, "big.txt")

Need just a key-value store?

Prefer AsyncStorage over serialising JSON into a file by hand; it's the native NSUserDefaults / SharedPreferences API and is async-first.

Notifications¶

Notifications schedules local notifications and cancels previously scheduled ones.

import pythonnative as pn


async def setup_reminder():
    granted = await pn.Notifications.request_permission()
    if not granted:
        return
    await pn.Notifications.schedule(
        title="Stretch break",
        body="Stand up!",
        delay_seconds=1800,
        identifier="reminder",
    )

request_permission() is required on iOS and on Android 13+. On older Android the call returns True without prompting.

For server-sent (remote) pushes, declare the remote_notifications capability in pythonnative.toml, then register with APNs:

token = await pn.Notifications.get_device_token()  # APNs hex token

Your server passes the token to APNs to address this install. The simulator has no APNs connection, so test on a real device. Android remote push requires a provider extension (Firebase Cloud Messaging), which the built-in module doesn't wire up; get_device_token() raises NativeModuleError("unsupported") there, and Platform.supports("Notifications", "get_device_token") reports it.

Clipboard¶

Clipboard reads and writes the system pasteboard synchronously.

import pythonnative as pn

pn.Clipboard.set_string("Copied!")
text = pn.Clipboard.get_string()
if pn.Clipboard.has_string():
    ...

Share.share presents the system share sheet and resolves to True once the user completes a share.

async def share_link():
    await pn.Share.share(message="Check this out", url="https://example.com")

Linking¶

Linking opens URLs, deep links, and the app's Settings page, and delivers inbound deep links to your app.

if pn.Linking.can_open_url("tel:+15551234567"):
    pn.Linking.open_url("tel:+15551234567")

launch_url = pn.Linking.get_initial_url()  # deep link the app opened with
pn.Linking.open_settings()                 # this app's entry in Settings

To receive deep links, declare your schemes in pythonnative.toml:

[app]
url_schemes = ["myapp"]

Opening myapp://orders/42 now launches (or foregrounds) your app on both platforms. The URL that cold-started the app is returned by get_initial_url(); URLs that arrive while the app is running reach subscribers:

unsubscribe = pn.Linking.add_listener(lambda url: navigate_to(url))

Permissions (runtime)¶

Permissions normalizes the iOS/Android permission models. Both check and request are coroutines (check reads asynchronous platform settings APIs; request prompts). Names are the [permissions] keys from pythonnative.toml that have a runtime prompt: "camera", "microphone", "photo_library", "location_when_in_use", "contacts", "notifications" (any other name raises ValueError). Statuses: "granted", "denied", "blocked", "undetermined".

if await pn.Permissions.check("camera") != "granted":
    status = await pn.Permissions.request("camera")
    if status == "blocked":
        pn.Linking.open_settings()  # user must enable it in Settings

Declaring the capability in [permissions] is what puts the usage string in the manifest; request is what shows the prompt.

App state¶

AppState reports the foreground/background lifecycle phase ("active", "inactive", "background"). Use the use_app_state hook in components:

@pn.component
def Status() -> pn.Node:
    state = pn.use_app_state()
    return pn.Text(f"App is {state}")

Outside the tree, subscribe imperatively:

unsubscribe = pn.AppState.add_listener(lambda s: print("now", s))

Network connectivity¶

NetInfo reports connectivity. fetch() returns {"is_connected": bool, "type": str, "is_internet_reachable": bool}; the use_net_info hook re-renders on change.

@pn.component
def Banner() -> pn.Node:
    net = pn.use_net_info()
    if not net["is_connected"]:
        return pn.Text("You are offline", style=pn.style(color="#B91C1C"))
    return pn.Spacer()

Secure storage¶

SecureStore persists secrets in the iOS Keychain / Android EncryptedSharedPreferences. Use it for tokens, not AsyncStorage, which is unencrypted.

pn.SecureStore.set_item("auth_token", token)      # raises NativeModuleError(code="write_failed")
token = pn.SecureStore.get_item("auth_token")     # None when absent
pn.SecureStore.delete_item("auth_token")          # raises NativeModuleError(code="delete_failed")

Both writers raise when the Keychain or EncryptedSharedPreferences reports failure (for example a Keychain entitlement problem) instead of returning False; deleting a key that isn't stored is not an error.

Battery¶

Battery exposes the charge level (0.0–1.0, or -1.0 if unknown) and state, plus a change listener.

level = pn.Battery.get_level()
state = pn.Battery.get_state()   # "charging" | "full" | "unplugged" | "unknown"

Haptics & vibration¶

Haptics plays semantic feedback; Vibration is a blunt duration-based buzz.

pn.Haptics.impact("medium")          # light | medium | heavy | soft | rigid
pn.Haptics.notification("success")   # success | warning | error
pn.Haptics.selection()
pn.Vibration.vibrate(400)            # milliseconds

Biometrics¶

Biometrics gates an action behind Face ID / Touch ID / fingerprint.

async def unlock():
    if pn.Biometrics.is_available() and await pn.Biometrics.authenticate("Unlock"):
        show_secrets()

Keyboard, dimensions, and pixel ratio¶

Keyboard reads and dismisses the on-screen keyboard. Native pushes a change event on every show, hide, and resize (iOS keyboardWillChangeFrame, Android WindowInsetsCompat.Type.ime()), which also feeds use_keyboard_height and KeyboardAvoidingView on both platforms:

pn.Pressable(pn.Text("Done"), on_press=pn.Keyboard.dismiss)
if pn.Keyboard.is_visible():
    ...
unsubscribe = pn.Keyboard.add_listener(lambda e: print(e.height, e.visible, e.duration_ms))

Dimensions and PixelRatio read the window and screen size and the display density. Neither talks to a native module: the screen host publishes width, height, scale, font_scale, screen_width, and screen_height on every layout pass, so both work anywhere, including outside components. Dimensions.add_listener delivers a DimensionsEvent with both window and screen, and fires only when a size or density changed:

window = pn.Dimensions.get("window")            # a WindowDimensions
screen = pn.Dimensions.get("screen")
columns = 3 if window.width >= 600 else 2

pn.PixelRatio.get()                              # 2.0 on a 2x display
pn.PixelRatio.get_font_scale()                   # the user's text-size multiplier
pn.PixelRatio.get_pixel_size_for_layout_size(1)  # whole pixels for 1 layout unit
hairline = pn.PixelRatio.round_to_nearest_pixel(0.5)

Inside a component prefer use_window_dimensions, which re-renders on change and now carries scale and font_scale too.

Device¶

Device.info returns one frozen DeviceInfo record: platform, os_version, model, manufacturer, is_simulator, is_tablet, app_name, app_version, build_number, bundle_id, scale, font_scale, and locale. Every key is filled on both platforms; the browser preview answers from navigator, and off device platform is "test":

info = pn.Device.info()
if info.is_tablet:
    columns = 3
print(f"{info.app_name} {info.app_version} ({info.build_number}) on {info.model}")

The writable data directory isn't part of DeviceInfo; use FileSystem.app_dir().

Localization¶

Localization reads the user's preferred languages and time zone (Locale.preferredLanguages on iOS, LocaleList.getDefault() on Android, navigator.languages in the browser). get_locales() returns Locale records (language_tag, language_code, region_code, is_rtl), most preferred first; get_timezone() returns the IANA name; and is_rtl() answers for the preferred locale. The use_locales hook re-renders when the user changes either setting:

locales = pn.Localization.get_locales()
tz = pn.Localization.get_timezone()             # "America/New_York"
direction = "rtl" if pn.Localization.is_rtl() else "ltr"

Accessibility info¶

AccessibilityInfo reads whether a screen reader or Reduce Motion is on, announces messages, and moves accessibility focus; the use_screen_reader_enabled and use_reduce_motion hooks are the reactive form. See Platform & Accessibility.

Writing your own native module¶

A native module has three parts: a Swift class, a Kotlin class, and a Python facade. The two native classes are registered under one name by a plugin entry (the same pn_plugin.json layout used for custom components); the facade calls them by that name and never imports platform code.

Native side¶

Each platform's base type is one method that settles a promise:

// native/ios/CompassModule.swift
import CoreLocation
import PythonNativeKit

public final class CompassModule: NSObject, PNNativeModule, CLLocationManagerDelegate {
    public static let name = "Compass"
    private let manager = CLLocationManager()
    private var pending: PNPromise?

    public override required init() {
        super.init()
        manager.delegate = self
    }

    public func call(_ method: String, args: [String: Any], promise: PNPromise) {
        switch method {
        case "is_available":
            promise.resolve(CLLocationManager.headingAvailable())
        case "heading":
            pending = promise               // settled later from the delegate
            manager.startUpdatingHeading()
        default:
            promise.reject("Compass has no method '\(method)'", code: "unknown_method")
        }
    }

    public func locationManager(_ manager: CLLocationManager, didUpdateHeading heading: CLHeading) {
        manager.stopUpdatingHeading()
        pending?.resolve(heading.trueHeading)
        pending = nil
    }
}

// native/android/com/example/compass/CompassModule.kt
package com.example.compass

import com.pythonnative.runtime.modules.NativeModule
import com.pythonnative.runtime.modules.Promise
import org.json.JSONObject

class CompassModule : NativeModule {
    override val name = "Compass"

    override fun call(method: String, args: JSONObject, promise: Promise) {
        when (method) {
            "is_available" -> promise.resolve(true)
            "heading" -> readHeadingOnce { degrees -> promise.resolve(degrees) }
            else -> promise.rejectUnknownMethod(method)
        }
    }
}

Settling the promise before call returns answers Python inline (a plain synchronous return). Settling it later, from any thread, delivers the result through the bridge's event channel to the Python application thread. Push unsolicited events with PNModuleEvents.emit(module:event:payload:) / ModuleEvents.emit(module, event, payload).

Register both in the plugin entry next to any component managers:

registry.registerModule(CompassModule.self)

registry.registerModule { CompassModule() }

Python facade¶

# compass/__init__.py
from typing import Optional

from pythonnative.native_modules.registry import native_module

_compass = native_module("Compass")


class Compass:
    @staticmethod
    def is_available() -> bool:
        return bool(_compass.call("is_available"))

    @staticmethod
    async def heading() -> float:
        return float(await _compass.call_async("heading"))

    @staticmethod
    def add_listener(callback) -> callable:
        return _compass.add_listener("change", callback)

call is for methods that answer inline; it raises NativeModuleError when native rejects. call_async awaits methods that settle later. add_listener subscribes to module events and returns an unsubscribe callable.

Follow the two rules the built-in facades follow: pick sync or async by what the OS does (a heading read is a coroutine here because the sensor has to spin up), and let NativeModuleError propagate rather than catching it and returning a placeholder. A caller who wants a fallback can write the try themselves; a caller who wanted to know it failed can't undo a swallowed exception.

Desktop and test implementation¶

native_module("Compass") returns a BridgeModule on device. Off device it looks for a Python implementation registered under the same name, so register one for pn preview and unit tests:

from pythonnative.native_modules.registry import register_python_module


class FallbackCompass:
    def is_available(self) -> bool:
        return False

    def heading(self) -> float:
        return 0.0


register_python_module("Compass", FallbackCompass())

Methods are looked up by name and called with the same keyword arguments the facade passed; a coroutine function is awaited by call_async. Packages register their desktop implementations through the pythonnative.modules entry point group so they are found without an explicit import:

[project.entry-points."pythonnative.modules"]
compass = "compass.desktop"

Tests can push module events directly with emit to exercise listeners without a device.

Next steps¶

Reference: Native modules API.
Async hooks and data fetching: Async + data.
See how device APIs interact with focus: Lifecycle.
Wrap a custom widget instead of an API: Custom native components.
Wire protocol and plugin layout: The native bridge.

Implementing an extension¶

Declare a Python protocol and generate its Python, Swift, and Kotlin interfaces. The generated adapters validate arguments and results, preserve nested records, and connect coroutine cancellation to the native operation. See generated native contracts and the separately packaged Inbox extension.