simplemonads 1.0.4

Simple Monads for Python. Use Just to end checking for None, Success to end unhandled exceptions, and Reader for dependency injection.

simplemonads

Simple Monads for Python. Use Just to end checking for None, Success to end unhandled exceptions, and Reader for dependency injection.

Example using monads: Success, Failure, Just, Reader, and Printer

from simplemonads import Success, Failure, Just, _, Reader, run, Printer

class AppDeps:
    def __init__(self, gui=Printer()):
        self.gui = gui
     
def app(divide_by_zero=False):                      
    data = Success(Just(7))     
    double = lambda x: x + (lambda y: y * 2)
    triple = lambda x: x + (lambda y: y * 3)
    result = data + triple + double  

    if divide_by_zero:
        result += (lambda x: x + (lambda x: x / 0))
    
    def effect(deps: AppDeps):
        return result | {
            Success:lambda x: x | {
                Just:lambda val: deps.gui.Popup('Answer to the Universe: ' + str(val))
            },
            Failure:lambda x: deps.gui.Popup('Whoops, an error happened: ' + x)
        } is result or result
    
    return Reader(effect)

class GuiAppDeps(AppDeps):
    def __init__(self, gui=Printer()):
        try:
            import PySimpleGUI
            self.gui = PySimpleGUI                        
        except:
            self.gui = gui
  
@run 
def main():        
    return app() + GuiAppDeps 

Handling exceptions

To demonstrate exception handling the above example can be changed to:

    return app(True) + GuiAppDeps

This will result in safely handling the divide by zero exception and will run the following without interrupting the flow of the application:

            Failure:lambda x: deps.gui.Popup('Whoops, an error happened: ' + x)