Use functools.singledispatch for Type-Based Extension Points in Python

Fri, 04 Sep 2026 00:00:00 +0700

A function often starts with one input type and later grows branches for several related types. The first version may be straightforward:

copied = false, 1600)" class="absolute right-3 top-3 z-10 rounded-lg border border-line-strong bg-surface px-2 py-1 font-mono text-[0.65rem] text-muted opacity-0 transition group-hover:opacity-100 hover:bg-ink hover:text-white dark:border-night-line dark:bg-night dark:text-night-muted dark:hover:bg-white dark:hover:text-ink">

def render(value):
    if isinstance(value, str):
        ...
    elif isinstance(value, list):
        ...
    elif isinstance(value, dict):
        ...

As the number of supported types grows, this function becomes the place where every extension must be added. The branches mix dispatch logic with the behavior for each type, and independently maintained modules cannot add support without editing the central function.

Extensibility on Nalar

Use functools.singledispatch for Type-Based Extension Points in Python