Py-Peeper

A very simple, minimalist, single-threaded and broadcast-routed approach to the observable pattern in Python.

Installation

pip install pypeeper

Usage

Implementing an Observable class

Every class can be converted to observable just by subclassing it from Observer. If class attribute "pattern" is overwritten with a valid regex expression, only matching attributes defined within the class constructor will be observed. Otherwise, all attributes will be observed.

from pypeeper import Observable, Observer

class AnyClass(Observable):

    def __init__(self):
        self.attribute_a = False
        self.whatever_attr = 0

    def set_attribute(self, value):
        self.attribute_a = value

Implementing an Observer class

Any class can be Observer of all Observable classes defined as shown above. To define how the class should react on Observable's changes, just override "notify" method from Observer class.

class ObserverClass(Observer):

    def notify(self, class_name, object_id, attribute_name, old, new):
        print(class_name, object_id, attribute_name, old, new)

Instantiate and play

my_observable = AnyClass()
my_observer = ObserverClass()

my_observable.set_attribute(True)
my_observable.attribute_a = 10
my_observable.whatever_attr = None

Console output

>>> AnyClass 2448221506696 attribute_a False True
>>> AnyClass 2448221506696 attribute_a True 10
>>> AnyClass 2448221506696 whatever_attr 0 None