Implementing concept of (Chain of responsability) design pattern, but linking handlers order by list object in different solutions

Chain of Responsability - Workflows.md

Object-oriented style

File: workflow_by_chain_of_responsability_oo.py

from abc import ABC, abstractmethod

#
# Abstract classes
#
class SharedAttributes:
    """ Empty object to store shared attributes among handlers """
    
    def __str__(self):
        return str(self.__dict__)


class Handler(ABC):
    @abstractmethod 
    def handle_request(self, request, shared_attributes): 
        pass


class Chain:
    handlers = tuple()

    def handle_request(self, request):
        # instantiate new shared attributes object
        self.shared_attributes = SharedAttributes()
        
        # instantiate handler class and execute method .handle_request()
        for handler_class in self.handlers:
            handler = handler_class()
            # execute handler request
            handler.handle_request(request=request, shared_attributes=self.shared_attributes)

        # return shared_attributes 
        return self.shared_attributes


#
# Concrete classes
#
class FirstWorkflowStep(Handler): 
    def handle_request(self, request, shared_attributes):
        shared_attributes.step = 'first'
        shared_attributes.x = 1
        print(f"-> Handling [request: {request}] [by: {self.__class__.__name__}] - shared attributes:", request, shared_attributes)


class SecondWorkflowStep(Handler): 
    def handle_request(self, request, shared_attributes):
        shared_attributes.step = 'second'
        shared_attributes.y = 2
        print(f"-> Handling [request: {request}] [by: {self.__class__.__name__}] - shared attributes:", request, shared_attributes)


class ThirdWorkflowStep(Handler): 
    def handle_request(self, request, shared_attributes):
        shared_attributes.step = 'third'
        shared_attributes.z = 3
        print(f"-> Handling [request: {request}] [by: {self.__class__.__name__}] - shared attributes:", request, shared_attributes)


class MySampleWorkflow(Chain):
    handlers = [
        FirstWorkflowStep,
        SecondWorkflowStep,
        ThirdWorkflowStep
    ]



if __name__ == "__main__" :    
    workflow = MySampleWorkflow() 

    requests = [ '1' , '2' , '3' ] 

    for request in requests: 
        print(f"Executing workflow for request: {request}") 
        workflow.handle_request(request) 
        print()

Executing:

$ python workflow_by_chain_of_responsability_oo.py

Executing workflow for request: 1
-> Handling [request: 1] [by: FirstWorkflowStep] - shared attributes: 1 {'step': 'first', 'x': 1}
-> Handling [request: 1] [by: SecondWorkflowStep] - shared attributes: 1 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 1] [by: ThirdWorkflowStep] - shared attributes: 1 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}

Executing workflow for request: 2
-> Handling [request: 2] [by: FirstWorkflowStep] - shared attributes: 2 {'step': 'first', 'x': 1}
-> Handling [request: 2] [by: SecondWorkflowStep] - shared attributes: 2 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 2] [by: ThirdWorkflowStep] - shared attributes: 2 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}

Executing workflow for request: 3
-> Handling [request: 3] [by: FirstWorkflowStep] - shared attributes: 3 {'step': 'first', 'x': 1}
-> Handling [request: 3] [by: SecondWorkflowStep] - shared attributes: 3 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 3] [by: ThirdWorkflowStep] - shared attributes: 3 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}

Functional style

File: workflow_by_chain_of_responsability_functional.py

from abc import ABC, abstractmethod

#
# Abstract classes
#
class SharedAttributes:
    """ Empty object to store shared attributes among handlers """
    
    def __str__(self):
        return str(self.__dict__)

class Chain:
    handlers = tuple()
    
    def __init__(self, handlers: tuple | None = None) -> None:
        self.handlers = handlers or self.handlers

    def handle_request(self, request):
        # instantiate new shared attributes object
        self.shared_attributes = SharedAttributes()
        
        # instantiate handler class and execute method .handle_request()
        for handler_function in self.handlers:
            # execute handler request
            handler_function(request=request, shared_attributes=self.shared_attributes)

        # return shared_attributes 
        return self.shared_attributes


def first_workflow_step(request, shared_attributes): 
    shared_attributes.step = 'first'
    shared_attributes.x = 1
    print(f"-> Handling [request: {request}] [by: first_workflow_step] - shared attributes:", request, shared_attributes)


def second_workflow_step(request, shared_attributes): 
    shared_attributes.step = 'second'
    shared_attributes.y = 2
    print(f"-> Handling [request: {request}] [by: second_workflow_step] - shared attributes:", request, shared_attributes)


def third_workflow_step(request, shared_attributes): 
    shared_attributes.step = 'third'
    shared_attributes.z = 3
    print(f"-> Handling [request: {request}] [by: third_workflow_step] - shared attributes:", request, shared_attributes)

class MySampleWorkflow(Chain):
    handlers = [
        first_workflow_step,
        second_workflow_step,
        third_workflow_step
    ]


if __name__ == "__main__" :
    # Define workflow
    workflow = MySampleWorkflow()
    
    ## Alternative way to declare the workflow directly without class
    # my_workflow_pipeline = [
    #     first_workflow_step,
    #     second_workflow_step,
    #     third_workflow_step
    # ]
    # workflow = Chain(handlers=my_workflow_pipeline)
    
    # Define requests
    requests = [ '1' , '2' , '3' ] 

    # Execute workflow process for each request
    for request in requests: 
        print(f"Executing workflow for request: {request}") 
        workflow.handle_request(request) 
        print()

Executing:

$ python workflow_by_chain_of_responsability_functional.py

Executing workflow for request: 1
-> Handling [request: 1] [by: first_workflow_step] - shared attributes: 1 {'step': 'first', 'x': 1}
-> Handling [request: 1] [by: second_workflow_step] - shared attributes: 1 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 1] [by: third_workflow_step] - shared attributes: 1 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}

Executing workflow for request: 2
-> Handling [request: 2] [by: first_workflow_step] - shared attributes: 2 {'step': 'first', 'x': 1}
-> Handling [request: 2] [by: second_workflow_step] - shared attributes: 2 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 2] [by: third_workflow_step] - shared attributes: 2 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}

Executing workflow for request: 3
-> Handling [request: 3] [by: first_workflow_step] - shared attributes: 3 {'step': 'first', 'x': 1}
-> Handling [request: 3] [by: second_workflow_step] - shared attributes: 3 {'step': 'second', 'x': 1, 'y': 2}
-> Handling [request: 3] [by: third_workflow_step] - shared attributes: 3 {'step': 'third', 'x': 1, 'y': 2, 'z': 3}