🍰 The little DI framework that tastes like a cake. 🍰

Documentation: https://fresh-bakery.readthedocs.io/en/latest/

Fresh Bakery

Fresh bakery is a lightweight [Dependency Injection][DI] framework/toolkit, which is ideal for building object dependencies in Python.

It is [fully] production-ready, and gives you the following:

• A lightweight, stupidly simple DI framework.
• Fully asynchronous, no synchronous mode.
• Any async backends compatible (asyncio, trio).
• Zero dependencies.
• Mypy compatible (no probably need for # type: ignore).
• FastAPI fully compatible.
• Litestar compatible.
• Pytest fully compatible (Fresh Bakery encourages the use of pytest).
• Ease of testing.
• Easily extended (contribution is welcome).

Requirements

Python 3.8+

Installation

$ pip3 install fresh-bakery

Examples

Quickstart

This example is intended to show the nature of Dependency Injection and the ease of use the library. Many of us work 8 hours per day on average, 5 days a week, i.e. ~ 40 hours per week. Let's describe it using DI and bakery:

from bakery import Bakery, Cake


def full_days_in(hours: int) -> float:
    return hours / 24


def average(total: int, num: int) -> float:
    return total / num


class WorkingBakery(Bakery):
    average_hours: int = Cake(8)
    week_hours: int = Cake(sum, [average_hours, average_hours, 7, 9, average_hours])
    full_days: float = Cake(full_days_in, week_hours)


async def main() -> None:
    async with WorkingBakery() as bakery:
        assert bakery.week_hours == 40
        assert bakery.full_days - 0.00001 < full_days_in(40)
        assert int(bakery.average_hours) == 8

You can see it's as simple as it can be.

One more example

Let's suppose we have a thin wrapper around file object.

from typing import ClassVar, Final

from typing_extensions import Self


class FileWrapper:
    file_opened: bool = False
    write_lines: ClassVar[list[str]] = []

    def __init__(self, filename: str) -> None:
        self.filename: Final = filename

    def write(self, line: str) -> int:
        type(self).write_lines.append(line)
        return len(line)

    def __enter__(self) -> Self:
        type(self).file_opened = True
        return self

    def __exit__(self, *_args: object) -> None:
        type(self).file_opened = False
        type(self).write_lines.clear()

This wrapper acts exactly like a file object: it can be opened, closed, and can write line to file. Let's open file hello.txt, write 2 lines into it and close it. Let's do all this with the bakery syntax:

from bakery import Bakery, Cake


class FileBakery(Bakery):
    _file_obj: FileWrapper = Cake(FileWrapper, "hello.txt")
    file_obj: FileWrapper = Cake(_file_obj)
    write_1_bytes: int = Cake(file_obj.write, "hello, ")
    write_2_bytes: int = Cake(file_obj.write, "world")


async def main() -> None:
    assert FileWrapper.file_opened is False
    assert FileWrapper.write_lines == []
    async with FileBakery() as bakery:
        assert bakery.file_obj.filename == "hello.txt"
        assert FileWrapper.file_opened is True
        assert FileWrapper.write_lines == ["hello, ", "world"]

    assert FileWrapper.file_opened is False
    assert FileWrapper.write_lines == []

Maybe you noticed some strange things concerning FileBakery bakery:

1. _file_obj and file_obj objects. Do we need them both?
2. Unused write_1_bytes and write_2_bytes objects. Do we need them?

Let's try to fix both cases. First, let's figure out why do we need _file_obj and file_obj objects?

• The first Cake for _file_obj initiates FileWrapper object, i.e. calls __init__ method;
• the second Cake for file_obj calls context-manager, i.e. calls __enter__ method on enter and __exit__ method on exit.

Actually, we can merge these two statements into single one:

# class FileBakery(Bakery):
    file_obj: FileWrapper = Cake(Cake(FileWrapper, "hello.txt"))

So, what about unused arguments? OK, let's re-write this gist a little bit. First, let's declare the list of strings we want to write:

# class FileBakery(Bakery):
    strs_to_write: list[str] = Cake(["hello, ", "world"])

How to apply function to every string in this list? There are several ways to do it. One of them is built-in map function.

map_cake = Cake(map, file_obj.write, strs_to_write)

But map function returns iterator and we need to get elements from it. Built-in list function will do the job.

list_cake = Cake(list, map_cake)

In the same manner as we did for file_obj let's merge these two statements into one. The final FileBakery will look like this:

class FileBakeryMap(Bakery):
    file_obj: FileWrapper = Cake(Cake(FileWrapper, "hello.txt"))
    strs_to_write: list[str] = Cake(["hello, ", "world"])
    _: list[int] = Cake(list, Cake(map, file_obj.write, strs_to_write))

The last thing nobody likes is hard-coded strings! In this case such strings are:

• the name of the file hello.txt
• list of strings to write: hello, and world

What if we've got another filename or other strings to write? Let's define filename and list of strings as FileBakery parameters:

from bakery import Bakery, Cake, __Cake__


class FileBakery(Bakery):
    filename: str = __Cake__()
    strs_to_write: list[str] = __Cake__()
    file_obj: FileWrapper = Cake(Cake(FileWrapper, filename))
    _: list[int] = Cake(list, Cake(map, file_obj.write, strs_to_write))

To define parameters you can use dunder-cake construction: __Cake__().
To pass arguments into FileBakery you can use native python syntax:

# async def main() -> None:
    async with FileBakeryMapWithParams(
        filename="hello.txt", strs_to_write=["hello, ", "world"]
    ) as bakery:
        ...

And the whole example will look like this:

from typing import ClassVar, Final

from typing_extensions import Self

from bakery import Bakery, Cake, __Cake__


# class FileWrapper: ...


class FileBakery(Bakery):
    filename: str = __Cake__()
    strs_to_write: list[str] = __Cake__()
    file_obj: FileWrapper = Cake(Cake(FileWrapper, filename))
    _: list[int] = Cake(list, Cake(map, file_obj.write, strs_to_write))


async def main() -> None:
    assert FileWrapper.file_opened is False
    assert FileWrapper.write_lines == []
    async with FileBakeryMapWithParams(
        filename="hello.txt", strs_to_write=["hello, ", "world"]
    ) as bakery:
        assert bakery.file_obj.filename == "hello.txt"
        assert FileWrapper.file_opened is True
        assert FileWrapper.write_lines == ["hello, ", "world"]

    assert FileWrapper.file_opened is False
    assert FileWrapper.write_lines == []

More examples are presented in section bakery examples.

Dependencies

No dependencies ;)

Changelog

You can see the release history here: https://github.com/Mityuha/fresh-bakery/releases/

Fresh Bakery is MIT licensed code.