observerutil 0.2.1

Let you implement observer pattern from the box

observerutil is simple and powerful observer pattern tool.

How to install

You could install from PyPi:

$ python3 -m pip install observerutil

Any callable can become observer

from typing import Any
from observerutil import Observers

def func_a():
    ...

def func_b():
    ...

observers = Observers([func_a])
observers.add(func_b)

observers.notify()

It is possible to provide any args and kwargs to observer

from typing import Any
from observerutil import Observers

def func_a(message: int):
    ...

observers = Observers()
observers.add(func_a)

# Distribute message to func_a.
# Any exceptions will be ignored.
message = 0
observers.notify(message)

from typing import Any
from observerutil import Observers

def func_a(**kwargs):
    ...

observers = Observers()
observers.add(func_a)

# Distribute kwargs to func_a.
# Any exceptions will be ignored.
observers.notify(user_id=123, role='client')

But in this case any exception will be ignored. If you would like to catch exceptions then use Observer with error handler.

from typing import Any
from observerutil import Observer, Observers, ErrorHandler


def func_a(message: int):
    print(100 / message)


def write_exception_to_logs(exc: Exception):
    ...


observer = Observer(func_a, error_handler=write_exception_to_logs)
observers = Observers()
observers.add(func_a)

message = 0
observers.notify(message)

If you would like to adapt message for observers in the collection then add message adapter

from typing import Any
from observerutil import Observers


def func_a(message: int):
    print(100 / message)


# parameters_adapter has to implement IParametersAdapter interface
def convert_to_int(*args, **kwargs):
    # exception of adapter is not catched by Observers instance.
    # add try...except here by self if required.
    return [int(arg) for arg in args], kwargs


observers = Observers(parameters_adapter=convert_to_int)
observers.add(func_a)

message = '2'
observers.notify(message)

More elegant way to convert each arg

from typing import Any
from observerutil import Observers, AdaptEachArg


def func_a(message: int):
    print(100 / message)

observers = Observers(parameters_adapter=AdaptEachArg(int))
observers.add(func_a)

message = '2'
observers.notify(message)