flex-dispatch 0.1.1

Dynamic dispatch for python similar to clojure's multimethod.

flex_dispatch

A super flexible dynamic dispatch implementation for python, inspired by Clojure's multimethod.

Install with: pip install flex-dispatch

To use: from flex_dispatch import Dispatcher and annotate any callable with @Dispatcher

Example

from flex_dispatch import Dispatcher


@Dispatcher
def greet(*args):
    if len(args) == 1:
        return '_just_name'
    elif len(args) == 2:
        return '_name_msg'


@greet.map('_just_name')
def say_hey(name):
    print(f'Hello, {name}!')


@greet.map('_name_msg')
def say_message(name, msg):
    print(f'{msg} {name}')


greet('Chris')   # calls say_hey and prints "Hello, Chris!"
greet('Bob', 'Boo')  # calls say_message and prints "Boo Bob"

greet('b', 'b', 3)  # greet returns none as a dispatch value, and DispatchError is raised.

Any callable decorated with @Dispatcher becomes a dispatcher function. It should inspect its arguments and return a "dispatch value"; i.e., a value used to determine which callable to dispatch the call to. Callables decorated with @<dispatcher>.map(<value>) (like @greet.map('_just_name') above) register the decorated function as the dispatch target for the given value.

In other words, when greet('Chris') is called, first the greet function is called to return a dispatch value, in this case '_just_name'. Since say_hey was decorated with @greet.amp('_just_name'), it was registered as the target function to call when greet returns the dispatch value '_just_name'.