Typesafe resource management in Python

This package creates a definition file by traversing the resource folder and parsing the files

Features

• Typesafe resource management (needs compatible type checker)
• Automatic type definition generation
• Middlewares, loaders api

PyPI: https://pypi.org/project/pathtyped/

pip install pathtyped

Showcase

This code can be found in demo

Your text files

resources/ data.json main.txt speech_0.txt speech_1.txt speech_2.txt

```py
# main.py
from pathtyped import *

rm = ResourceManager(
    f"resources",
    DefinitionFile("", f"resource_definition.py"),
    [remove_known_extensions(r"txt|json"), group_by(r"(speech)_(\d)")],
    [Loaders.text, Loaders.json],
)

from resource_definition import root

resource: root = rm.root  # type: ignore
# The file below does not exist yet
from definition import root

resource: root = resource_manager.root # type: ignore

# defaults.py
# No need to import anything since type str is already imported
# Example
from some_code import YourClass

Generates

# 8587d74aed20f794cdfc800f26c456b7
# Automatically generated by ResourceManager at: 2023-01-15 23:37:27.451164
# DO NOT EDIT THIS FILE MANUALLY. 
# If you want to regenerate this file, change the integrity hash in the first line to something else

# Some generic fixes
list = list[object]
dict = dict[object, object]

# Default import statement:

# Main content:
from typing import NamedTuple

root = NamedTuple("root", [
    ("speech", tuple[
        str,
        str,
        str,
    ],),
    ("data", dict),
    ("main", str),
])

And provides you with type compilation

Documentation

Middlewares

Middlewares are functions that have the ability to modify the tree structure itself as well as change the value of the nodes

They are applied in the order they are passed to the ResourceManager, with each middleware doing a full DFS preorder traversal of the tree

for middleware in middlewares:
    # The @middleware decorator will initiate the dfs preorder traversal
    tree = middleware(self, "<root>", tree)

This also means that the middleware will be applied to the leaf of the trees that it has returned. This is the most desirable behavior for applying middlewares

@middleware
def strip_numbers_in_string(r: ResourceManager, location: str, tree: EntryTree) -> Optional[EntryTree]:
    """Removes all number property from tree"""
    if isinstance(tree, EntryDict):
        new_tree = EntryDict()
        for key in list(tree.keys()):
            n = re.sub(r"\d+", "", key)
            new_tree[n] = tree[key]
        # If a new dict or list is returned, it will replace the old one
        # Be sure to return a new EntryTree
        return new_tree
    # Returning None indicates that the tree should not be changed
    # You can also modify tree in place and it will be reflected
    return None

Loaders

Loaders are simpler middlewares. They are functions that only take the leaf node and transform it into a useful value.

Most leaf nodes are Path objects

The resource manager will attempt to apply each loader to the leaf node in the order they are passed to the ResourceManager. Returning None indicates that the loader does not know how to handle the leaf node and will pass it to the next loader

for loader in self.loaders:
    if (r := loader(self, obj)) is not None:
        return r

If you want multiple loaders to be applied the same leaf node see the example code at the bottom

# Basic loaders
@loader
def return_suffix(r: ResourceManager, path: Path) -> str:
    return path.suffix

@loader
@extension("mp3")
def pygame_load(r: ResourceManager, path: Path) -> pygame.mixer.Sound:
    return pygame.mixer.Sound(path)

fallback_image = pygame.image.load("fallback.png")

@loader
@extension(r"png|jpg|jpeg")
@fallback(fallback_image) # If the loading raises an Exception
def pygame_image_load(r: ResourceManager, path: Path) -> pygame.Surface:
    return pygame.image.load(path)

# Advanced loaders

# Loader that accepts certain object nodes
# Requires a compatible middleware to generate such leaves
@loader(Script)
def execute(r: ResourceManager, s: Script) -> object:
    return s.execute()

# Two transformations
@loader
def str_node(r: ResourceManager, path: Path) -> str:
    return path.read_text()

@loader(str)
def str_to_int(r: ResourceManager, s: str) -> int:
    if s.isnumeric():
        return int(s)

@loader
def combined(r: ResourceManager, path: Path) -> Union[str, int]:
    res = path
    for l in [str_node, str_to_int]:
        if (t := l(r, res)) is not None:
            res = t
    return res

FAQ

Visual Studio Code shows that the type is any

Change the python.analysis.typeCheckingMode setting to strict and it not allow you to access invalid properties. Make sure that the Python language server is Pylance

{
    "python.analysis.typeCheckingMode": "strict"
}

Cannot import TypeGuard

Project requires Python 3.10 or higher

Contributing

If you have an idea for this library, please make an issue first instead of a PR. I will be happy to discuss it with you