Why make this?

TL;DR: I like nice types and I wanted to try mkdocs.

Python's Sum

Python's current sum function requires types to choose one of the following:

# The bad: verbose calls
sum(iterable, start_value)

This allows type annotations to be clean, but it feels bad.

# The ugly: gross type annotations
class SupportsSum:

    # int is ugly
    def __radd__(self, other: int | SupportsSum):
        if other == 0:
            return self
        ...

This allows short sum calls, but it feels wrong from a type checking perspective.

Trying Mkdocs

I've used Sphinx while working on Arcade and pyglet, but I wanted to explore other documentation systems.

Other Inspiration

As of pyglet 2.1's dev previews, pyglet.math contains:

1. comments explaining how Pythons' sum uses 0 as a start value
2. pyglet.math types which support sum by allowing __radd__ to take an int value.