remi 1.2.1

Python REMote Interface library

A Platform independent Python GUI library for your applications

Remi is a GUI library for Python applications which transpiles an application's interface into HTML to be rendered in a web browser. This removes platform-specific dependencies and lets you easily develop cross-platform applications in Python!

Do you need support? Reach us on:

Reddit - (subreddit RemiGUI)

Changelog

The current branch includes a bunch of updates. The major changes are related to the event infrastructure. Now, an event listener can be registered as:

widget.eventname.connect(listener)

instead of:

widget.set_on_xxx_listerner(listener)

And so, in order to register a listener for the onclick event you can do button.onclick.connect(myapp.on_button_pressed) .

The previous dialect is still compatible.

Getting Started

For a stable version:

pip install remi

For the most updated experimental version Download or check out Remi from git and install

python setup.py install

or install directly using pip

pip install git+https://github.com/dddomodossola/remi.git

Then start the test script:

python widgets_overview_app.py

Remi

Platform independent Python GUI library. In less than 100 Kbytes of source code, perfect for your diet.

Remi enables developers to create platform independent GUI with Python. The entire GUI is converted to HTML and is rendered in your browser. No HTML is required, Remi automatically translates your Python code into HTML. When your app starts, it starts a webserver that will be accessible on your network.

A basic application appears like this:

import remi.gui as gui
from remi import start, App

class MyApp(App):
    def __init__(self, *args):
        super(MyApp, self).__init__(*args)

    def main(self):
        container = gui.VBox(width = 120, height = 100)
        self.lbl = gui.Label('Hello world!')
        self.bt = gui.Button('Press me!')

        # setting the listener for the onclick event of the button
        self.bt.onclick.connect(self.on_button_pressed)

        # appending a widget to another, the first argument is a string key
        container.append(self.lbl)
        container.append(self.bt)

        # returning the root widget
        return container

    # listener function
    def on_button_pressed(self, widget):
        self.lbl.set_text('Button pressed!')
        self.bt.set_text('Hi!')

# starts the webserver
start(MyApp)

In order to see the user interface, open your preferred browser and type "http://127.0.0.1:8081". You can change the url address by specific **kwargs at start function call. This will be discussed later.

Tested on Android, Linux, Windows. Useful on Raspberry Pi for Python script development. It allows to interact with your Raspberry Pi remotely from your mobile device.

FAQ

• Why another GUI lib?
  Kivy, PyQT and PyGObject all require native code for the host operating system, which means installing or compiling large dependencies. Remi needs only a web browser to show your GUI.

• Do I need to know HTML?
  NO, It is not required, you have to code only in Python.

• Which browsers can I use this with?
  Tested on Chrome Firefox and Edge (on Windows, Linux and Android) and haven't tested it elsewhere. It will probably work fine elsewhere though!

• Is it open source?
  For sure! Remi is released under the Apache License. See the LICENSE file for more details.

• Do I need some kind of webserver? No, it's included.

Brief tutorial

Import Remi library and some other useful stuff.

import remi.gui as gui
from remi import start, App

Subclass the App class and declare a main function that will be the entry point of the application. Inside the main function you have to return the root widget.

class MyApp( App ):
	def __init__( self, *args ):
		super( MyApp, self ).__init__( *args )

	def main( self ):
		lbl = gui.Label( "Hello world!", width=100, height=30 )

		#return of the root widget
		return lbl

Outside the main class start the application calling the function start passing as parameter the name of the class you declared previously.

#starts the webserver	
start( MyApp )

Run the script. If all it's OK the gui will be opened automatically in your browser, otherwise you have to type in the address bar "http://127.0.0.1:8081".

You can customize optional parameters in the start call like.

start(MyApp,address='127.0.0.1', port=8081, multiple_instance=False, enable_file_cache=True, update_interval=0.1, start_browser=True) 

Parameters:

• address: network interface ip
• port: listen port
• multiple_instance: boolean, if True multiple clients that connects to your script has different App instances (identified by unique cookie session identifier)
• enable_file_cache: boolean, if True enable resource caching
• update_interval: gui update interval in seconds. If zero, the update happens at each change. If zero, the App.idle method is not called.
• start_browser: boolean that defines if the browser should be opened automatically at startup
• standalone: boolean, indicates where to run the application as standard Desktop application with its own window. If False, the interface is shown in a browser webpage.

Additional Parameters:

• username: for a basic http authentication
• password: for a basic http authentication
• host_name: the server hostname
• certfile: ssl certificale filename
• keyfile: ssl key file
• ssl_version: authentication version (i.e. ssl.PROTOCOL_TLSv1_2). If None, disables ssl encription

All widgets constructors accepts two standard **kwargs that are:

• width: can be expressed as int (and is interpreted as pixel) or as str (and you can specify the measure unit like '10%')
• height: can be expressed as int (and is interpreted as pixel) or as str (and you can specify the measure unit like '10%')

Events and callbacks

Widgets exposes a set of events that happens during user interaction. Such events are a convenient way to define the application behavior. Each widget has its own callbacks, depending on the type of user interaction it allows. The specific callbacks for the widgets will be illustrated later.

In order to register a function as an event listener you have to call a function like eventname.connect (i.e. onclick.connect) passing as parameters the callback that will manage the event. Follows an example:

import remi.gui as gui
from remi import start, App

class MyApp(App):
    def __init__(self, *args):
        super(MyApp, self).__init__(*args)

    def main(self):
        container = gui.VBox(width = 120, height = 100)
        self.lbl = gui.Label('Hello world!')
        self.bt = gui.Button('Press me!')

        # setting the listener for the onclick event of the button
        self.bt.onclick.connect(self.on_button_pressed)

        # appending a widget to another, the first argument is a string key
        container.append(self.lbl)
        container.append(self.bt)

        # returning the root widget
        return container

    # listener function
    def on_button_pressed(self, widget):
        self.lbl.set_text('Button pressed!')
        self.bt.set_text('Hi!')

# starts the webserver
start(MyApp)

In the shown example self.bt.onclick.connect(self.on_button_pressed) registers the self's on_button_pressed function as a listener for the event onclick exposed by the Button widget. Simple, easy.

Listener's callbacks will receive the emitter's instance firstly, then all other parameters provided by the specific event.

Beside the standard event registration (as aforementioned), it is possible to pass user parameters to listener functions. This can be achieves appending parameters to the connect function call.

import remi.gui as gui
from remi import start, App

class MyApp(App):
    def __init__(self, *args):
        super(MyApp, self).__init__(*args)

    def main(self):
        container = gui.VBox(width = 120, height = 100)
        self.lbl = gui.Label('Hello world!')
        self.bt = gui.Button('Hello name!')
        self.bt2 = gui.Button('Hello name surname!')

        # setting the listener for the onclick event of the buttons
        self.bt.onclick.connect(self.on_button_pressed, "Name")
        self.bt2.onclick.connect(self.on_button_pressed, "Name", "Surname")

        # appending a widget to another
        container.append(self.lbl)
        container.append(self.bt)
        container.append(self.bt2)

        # returning the root widget
        return container

    # listener function
    def on_button_pressed(self, widget, name='', surname=''):
        self.lbl.set_text('Button pressed!')
        widget.set_text('Hello ' + name + ' ' + surname)

# starts the webserver
start(MyApp)

This allows great flexibility, getting different behaviours with the same event listener definition.

HTML Attribute accessibility

Sometimes could be required to access Widget's HTML representation in order to manipulate html attributes. The library allows to access these information easily.

A simple example: It is the case where you would like to add an hover text to a widget. This can be achieved by the title attribute of an html tag. In order to do this:

    widget_instance.attributes['title'] = 'Your title content'

A special case of html attribute is the style. The style attributes can be altered in this way:

    widget_instance.style['color'] = 'red'

The assignment of a new attribute automatically creates it.

Take care about internally used attributes. These are:

• class: It is used to store the Widget class name for styling purpose
• id: It is used to store the instance id of the widget for callback management

Remote access

If you are using your REMI app remotely, with a DNS and behind a firewall, you can specify special parameters in the start call:

• port: http server port. Don't forget to NAT this port on your router;
• host_name: a string containing the host name or remote ip address that allows to access to your app.

start(MyApp, address='0.0.0.0', port=8081, host_name='myhostname.net') 

Standalone Execution

I suggest to use the browser as standard interface window.

However, you can avoid using the browser. This can be simply obtained joining REMI and PyWebView. Here is an example about this standalone_app.py.

Be aware that PyWebView uses qt, gtk and so on to create the window. An outdated version of these libraries can cause ui problems. If you experience ui issues, update these libraries, or better avoid standalone execution.

Authentication

In order to limit the remote access to your interface you can define a username and password. It consists in a simple authentication process. Just define the parameters username and password in the start call:

start(MyApp, username='myusername', password='mypassword') 

Styling

In order to define a new style for your app you have to do the following. Create a res folder and pass it to your App class constructor:

class MyApp(App):
    def __init__(self, *args):
        res_path = os.path.join(os.path.dirname(__file__), 'res')
        super(MyApp, self).__init__(*args, static_file_path=res_path)

Make a copy the standard style.css from the remi folder and paste it inside your res folder. Edit it in order to customize. This way the standard style.css file gets overridden by the one you created.

Compatibility

Remi is made to be compatible from Python2.7 to Python3.X . Please notify compatibility issues.

Security

Remi should be intended as a standard desktop gui framework. The library itself doesn't implement security strategies, and so it is advised to not expose its access to unsafe public networks.

When loading data from external sources, consider protecting the application from potential javascript injection before displaying the content directly.

Supporting the project

Are you able to support the Remi project?

Are you aware that remi is on Patreon? That's a brilliant way to support this project.

SUPPORT Remi now

Also a small amount is really welcome.

Contributors

Thank you for collaborating with us to make Remi better! The real power of opensource are contributors. Please feel free to partecipate to this project, and consider to add yourself to the following list. Yes I know that github already provides a list of contributors, but I feel that I must mention who helps.

Davide Rosa

John Stowers

Claudio Cannatà

Sam Pfeiffer

Ken Thompson

Paarth Tandon

Ally Weir

Timothy Cyrus

John Hunter Bowen

Martin Spasov

Wellington Castello

PURPORC

ttufts

Chris Braun

Alan Yorinks

Bernhard E. Reiter

saewoonam

Projects using Remi

Web based dynamic reconfigure for ROS robots

razmq

Espresso-ARM

PiPresents

The Python Banyan Framework

Other Implementations

Here are listed other implementations of this library:

• cremi: (WIP) developed for your C++ projects by Claudio Cannatà.