The Power of Polymorphism in Python

The Secret Sauce Behind Julia and Lisp — Now in Python

Photo by BHLNZ - Biodiversity Heritage Library NZ on Unsplash — Multiple Dispatch comes with Polymorphism — treating different combinations of function argument types in a different way — under the same function/method name

Have you ever wished your Python functions could respond more smartly — like really smartly — depending on all the argument types passed in? That’s multiple dispatch. It’s like function overloading’s cooler, more flexible cousin, and it’s built into languages like Julia and Common Lisp (via CLOS). But in Python? Well, it takes some extra work.

Let me take you on a little journey — story-first, code-always — to show you what works, what doesn’t, and what will save you time and sanity.

Part 1: Trying multipledispatch (And Seeing Where It Cracks)

Let’s say we’re writing a program that greets people differently based on whether they’re Vegan, Vegetarian, or just a regular Person. Sounds easy?

Let’s start with the multipledispatch package:

from multipledispatch import dispatch

class Person:
    pass

class Vegan(Person):
    pass

class Vegetarian(Person):
    pass

@dispatch(Vegan, str)
def greet(person, name):
    return f"Hi, I'm {name}! I'm a vegan!"

@dispatch(Vegetarian, str)
def greet(person, name):
    return f"Hi, I'm {name}! I'm a vegetarian!"

@dispatch(Person, str)
def greet(person, name):
    return f"Hi, I'm {name}…