apfel.impt.transform

This module provides a low-level hook mechanism to transform the source code of a package or module during its import. It must be imported before any other packages and modules that you want to hook.

Warning

Effectful

This package has an effectful behavior: modifying the sys.meta_path finder list, which will affect the import process, and is sensitive to the order of imports.

Normally you would use adapters defined in the impt package, instead of directly using the low level register_transform_hook function.

API#

Classes

Name	Description
TransformPathFinder	A subclass of :python importlib.machinery.PathFinder
TransformSourceFileLoader	A subclass of :python importlib.machinery.SourceFileLoader

Functions

Name	Description
register_transform_hook	Register a hook function to replace the source code of a module or package.

TransformPathFinderclass#

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class TransformPathFinder(_frozen_importlib_external.PathFinder)

Bases: _frozen_importlib_external.PathFinder

A subclass of importlib.machinery.PathFinder that injects TransformSourceFileLoader to the import process.

find_specmethodclassmethod#

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def find_spec(fullname: str, path: Sequence[str] | None = None, target: ModuleType | None = None) -> importlib.machinery.ModuleSpec | None

TransformSourceFileLoaderclass#

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class TransformSourceFileLoader(fullname: str, path: str, *, hook: Sequence[Callable[[str], str]])

Bases: _frozen_importlib_external.SourceFileLoader

A subclass of importlib.machinery.SourceFileLoader that applies all registered hooks to the source code of a module or package during import.

Note

This loader will directly read the source code from the .py file, completely ignoring the .pyc file. The transformed source code will not have a bytecode cache (.pyc) generated. If your file system has high latency, this may slow down the import process.

hookattributeinstance attribute#

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hook = hook

__init__method#

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def __init__(fullname: str, path: str, *, hook: Sequence[Callable[[str], str]]) -> None

get_datamethod#

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def get_data(path: str) -> bytes

set_datamethod#

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def set_data(path, data, *, _mode: int = 438)

register_transform_hookfunction#

View source

def register_transform_hook(name: str, hook: Callable[[str], str]) -> None

Register a hook function to replace the source code of a module or package.

Parameters

Name	Type	Description
name	str	The name of the module or package to hook.
hook	Callable[[str], str]	The hook function that takes the original source code as input and returns the transformed source code.