Py-Undefined

A light-weight library providing an Undefined type to Python.

Install

Py-Undefined is on PyPI and can be installed with:

pip install py-undefined

Or with Poetry

poetry add py-undefined

Usage

The Undefined class from this module can be used as a variable type and a value.

from py_undefined import Undefined

a: Undefined | int = Undefined

assert a is Undefined

Why?

This is very useful to web frameworks that need to distinguish between receiving null as a parameter value vs not receiving that parameter at all.

Example

# Framework that can now pass `Undefined` instead of `None` to method if param was absent from request.
@framework.method()
def update(a: int | Undefined, b: int | None | Undefined) -> None:
    if a is not Undefined:
        ...
    if b is not Undefined:
        ...

This allows for a client to use this method to update only what values are provided.

my_client.update(b=1)  # Set b.
my_client.update(a=2)  # Set a without setting b to None.
my_client.update(b=None)  # b can be set to None explicitly.

Support The Developer