A tale of two cellphones: Python on Android and iOS

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A tale of two cellphones Python on Android and iOS Dr Russell Keith-Magee @freakboy3742 PyCon US 2016

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A tale of two cellphones Python on Android and iOS Dr Russell Keith-Magee @freakboy3742 PyCon US 2016

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What is "Mobile Python"?

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A native application delivered as a native application using native system APIs.

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A native application...

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... delivered as a native application ...

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... using native system APIs.

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What is currently possible?

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What is currently possible? You can: Write a native iOS application Write a native Android application Write a cross-platform application

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iOS

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CPython Issue 23670

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Using CPython on iOS

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Python-iOS-template Cookiecutter http://github.com/pybee/Python-iOS-template

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Accessing native libraries

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Swift

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Objective C NSURL *url = [NSURL URLWithString:@"http://pybee.org"];

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Objective C (intermediate) NSString *str = [ [NSString alloc] initWithCharacters:"http://pybee.org" length:16 ]; NSURL *url = [NSURL URLWithString:str];

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Objective C in C Class nsstring = objc_getClass("NSString"); SEL alloc = sel_registerName("alloc"); id str = objc_msgsend(nsstring, alloc); SEL init = sel_registerName( "initWithCharacters:length:"); str = objc_msgsend( str, init, "http://pybee.org", 16); Class nsurl = objc_getClass("NSURL"); SEL urlwithstring = sel_registerName( "URLWithString:"); id url = objc_msgsend( nsurl, urlwithstring, str);

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ctypes from ctypes import * libc = cdll.LoadLibrary("libc.so.6") libc.strchr.argtypes = [c_char_p, c_char] libc.strchr.restype = c_char_p >>> print(libc.strchr(b"abcdef", b"d")) 'def'

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ctypes and Objective C from ctypes import * lib = util.find_library(b'objc') objc = cdll.LoadLibrary(lib) objc.objc_getClass.argtypes = [c_char_p] objc.objc_getClass.restype = c_void_p NSString = objc.objc_getClass(b'NSString')

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Descriptors class ObjCInstance: def __getattr__(self, name): print("Getting attribute", name) def __setattr__(self, name, value): print("Set", name, "to", value) >>> obj = ObjCInstance() >>> obj.spam Getting attribute spam >>> obj.pork = "ham" Set attribute pork to ham

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Callables class Method: def __call__(self, *args) print("Invoke method with args", args) ... >>> method = Method() >>> method(1,2,3) Invoke method with args (1, 2, 3)

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Object creation class Method: def __new__(cls, *args) ...

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Rubicon

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Rubicon from ctypes import cdll, util from rubicon.objc import ObjCClass cdll.LoadLibrary(util.find_library('Foundation')) NSURL = ObjCClass('NSURL'); NSURL.URLWithString_("http://pybee.org/")

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Rubicon from rubicon.objc import * NSObject = ObjCClass(NSObject) class Handler(NSObject): @objc_method def initWithValue_(self, v: int): self.value = v return self @objc_method def pokeWithValue_(self, v: int) -> None: print ("Poking with", v)

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An iOS application in Python class PythonAppDelegate(UIResponder): @objc_method def application_didFinishLaunchingWithOptions_( self, application, launchOptions) -> bool: ... class MyViewController(UIViewController): @objc_method def loadView(self) -> None: self.title = 'Add item'

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Android

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CPython Issue 23496 https://bitbucket.org/xdegaye/pyona/src

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Jython

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Rethinking the problem

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Inside Python def sing(): for i in range(100, 0, -1): print("%d bottles of beer on the wall" %i) print()

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Python Bytecode import dis dis.dis(sing)

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Bytecode 2 0 SETUP_LOOP 47 (to 50) 3 LOAD_GLOBAL 0 (range) 6 LOAD_CONST 1 (100) 9 LOAD_CONST 2 (0) 12 LOAD_CONST 5 (-1) 15 CALL_FUNCTION 3 (3 positional, 0 keyword pair) 18 GET_ITER >> 19 FOR_ITER 27 (to 49) 22 STORE_FAST 0 (i) 3 25 LOAD_GLOBAL 1 (print) 28 LOAD_CONST 4 ('%d bottles of beer on the wall') ...

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Java package com.example; public class Sing { public static void main(String [] args) { for (int i = 100; i < 0; i--) { System.out.println(i + " bottles of beer on the wall"); } } }

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Bytecode Max stack: 3 Max locals: 2 Bytecode: (39 bytes) 0: BIPUSH 100 2: ISTORE_1 3: ILOAD_1 4: IFGE 34 7: GETSTATIC java/lang/System.out 10: NEW java/lang/StringBuilder 13: DUP 14: INVOKESPECIAL java/lang/StringBuilder. 17: ILOAD_1 ...

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VOC

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An Android application in Python from android.widget import ListView class MainActivity( extends=android.app.Activity): def onCreate(self, state: android.os.Bundle ) -> void: super().onCreate(state) Log.i("MyApp", "Create new app") listview = ListView(self) ...

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Python-Android-template Cookiecutter http://github.com/pybee/Python-Android-template

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Cross platform

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Kivy

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Toga

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A Toga App import toga class TodoApp(toga.App): def startup(self): self.list = toga.List( data=[...], on_delete=self.remove_entry, on_refresh=self.refresh ) ...

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A Toga App (pt II) ... container = toga.NavigationView( title="Todo List", content=self.list, on_action=self.show_add_dialog ) self.main_window.content = container

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A Toga App (pt III) ... self.input = toga.TextInput(placeholder="thing to do...") self.add_item_dialog = toga.Dialog( title="Add item", content=toga.Container( self.input ), on_accept=self.add_entry ) ...

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A Toga App (pt IV) def show_add_dialog(self, widget): self.input.clear() self.show_dialog(self.add_item_dialog) def add_entry(self, widget): if self.input.value: self.list.add({'description': self.input.value}) def remove_entry(self, widget): ... def refresh(self, list_widget): ...

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bit.ly/toga-mobile-demo

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Packaging

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pip install briefcase python setup.py ios python setup.py android

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The future

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The threat

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The opportunity

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It is the best of times, it is the worst of times, it is the age of wisdom, it is the age of foolishness, it is the epoch of belief, it is the epoch of incredulity...

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Thank you! [email protected] @freakboy3742 pybee.org @PyBeeWare Python Mobile-SIG