njct

Njct is a bare-bones dependency injection utility. I wrote it some time ago for a small project.

without njct:

def fetch_news():
    if config["news_source"] == "foo":
        news = Foo().get_news()
    elif config["news_source"] == "bar":
        import bar
        news = bar.get_news()

with njct:

@njct.provider()
class News(Protocol):
    def get_news(): ...

def fetch_news(provider: News.inject):
    news = provider.get_news()

fetch_news(News()) # Automatically select an implementation
fetch_news(News["bar"]()) # or specify one manually

To learn more, see examples/json_provider.py

caveats

Njct is not production ready.

In particular, it assumes all implementations have the same __init__() signature, making custom config per implementation difficult (though, not impossible).

Njct is also non-intrusive. Most of it's features are type-level. In particular, njct does not interfere with instantiation or state at all. This may be underwhelming if you're used to the magic of proper DI frameworks.