Python .on event triggers

"""
You need to use the Observer Pattern (http://en.wikipedia.org/wiki/Observer_pattern). 
In the following code, a person subscribes to receive updates from the global wealth entity. 
When there is a change to global wealth, this entity then alerts all 
its subscribers (observers) that a change happened. Person then updates itself.

I make use of properties in this example, but they are not necessary. 
A small warning: properties work only on new style classes, so 
the (object) after the class declarations are mandatory for this to work.
"""


class GlobalWealth(object):
    def __init__(self):
        self._global_wealth = 10.0
        self._observers = []

    @property
    def global_wealth(self):
        return self._global_wealth

    @global_wealth.setter
    def global_wealth(self, value):
        self._global_wealth = value
        for callback in self._observers:
            print('announcing change')
            callback(self._global_wealth)

    def bind_to(self, callback):
        print('bound')
        self._observers.append(callback)


class Person(object):
    def __init__(self, data):
        self.wealth = 1.0
        self.data = data
        self.data.bind_to(self.update_how_happy)
        self.happiness = self.wealth / self.data.global_wealth

    def update_how_happy(self, global_wealth):
        self.happiness = self.wealth / global_wealth


if __name__ == '__main__':
    data = GlobalWealth()
    p = Person(data)
    print(p.happiness)
    data.global_wealth = 1.0
    print(p.happiness)

Source: stackoverflow.com

Similar codes

12 votes238 views4 answers
Couldn't find a tree builder with the features you requested: lxml. Do you need to install a parser library?
Python
0 vote187 views1 answer
How to fetch only the columns from a datframe which has a particular datatype
Python
0 vote188 views1 answer
Starting variable name with underscore python
Python
0 vote203 views1 answer
Csrf token fetch django
Python
3 votes189 views2 answers
Merge sort of two list in python
Python
0 vote187 views0 answer
Python
0 vote191 views2 answers
Class chain methods python
Python
0 vote170 views1 answer
Save a seaborn heatmap
Python
0 vote186 views2 answers
Try except in list comprehension
Python
0 vote175 views1 answer
Creating a Pandas Data Frame Series
Python