example.py

import json
from eventdispatcher import EventDispatcher, Property, ListProperty


class SettingsFile(EventDispatcher):
    last_login = Property(None)
    color = Property('red')

    def __init__(self, filepath):
        super(SettingsFile, self).__init__()
        self.filepath = filepath
        self.number_of_file_updates = 0
        # Bind the properties to the function that updates the file
        self.bind(last_login=self.update_settings_file,
                  color=self.update_settings_file)

    def on_last_login(self, inst, last_login):
        # Default handler for the last_login property
        print 'last login was %s' % last_login

    def on_color(self, inst, color):
        # Default handler for the color property
        print 'color has been set to %s' % color

    def update_settings_file(self, *args):
        # Update the file with the latest settings.
        print 'Updating settings file.'
        self.number_of_file_updates += 1
        with open(self.filepath, 'w') as _f:
            settings = {'last_login': self.last_login, 'color': self.color}
            json.dump(settings, _f)



if __name__ == '__main__':

    s = SettingsFile('./myfile.json')
    s.last_login = 'May 18 2015'                                        # Updates settings file
    s.last_login = 'May 18 2015'                                        # Does not update settings file
    s.color = 'blue'                                          # Updates settings file
    s.color = 'blue'                                          # Does not update settings file


    print 'The file was updated %d times' % s.number_of_file_updates


    file1 = SettingsFile('./myfile1.json')
    file2 = SettingsFile('./myfile2.json')

    # Binds the color property from file1 to the color property of file2
    # Changing file1.color will automatically update the value of file2.color
    file1.bind(color=file2.setter('color'))

    file1.color = 'green'