importlib.resources

This repository is to house the design and implementation of a planned importlib.resources module for Python's stdlib -- aiming for Python 3.7 -- along with a backport to target Python 3.4 - 3.6.

The key goal of this module is to replace pkg_resources with a solution in Python's stdlib that relies on well-defined APIs. This should not only make reading resources included in packages easier, but have the semantics be stable and consistent.

Goals

• Provide a reasonable replacement for pkg_resources.resource_stream()
• Provide a reasonable replacement for pkg_resources.resource_string()
• Provide a reasonable replacement for pkg_resources.resource_filename()
• Define an ABC for loaders to implement for reading resources
• Implement this in the stdlib for Python 3.7
• Implement a package for PyPI which will work on Python >=3.4

Non-goals

• Replace all of pkg_resources
• For what is replaced in pkg_resources, provide an exact replacement

Design

Low-level

For importlib.abc:

from typing import Optional
from typing.io import BinaryIO


class ResourceReader(abc.ABC):

    def open_resource(self, path) -> BinaryIO:
        """Return a file-like object opened for binary reading.

        The path is expected to be relative to the location of the
        package this loader represents.
        """
        raise FileNotFoundError

    def resource_path(self, path) -> str:
        """Return the file system path to the specified resource.

        If the resource does not exist on the file system, raise
        FileNotFoundError.
        """
        raise FileNotFoundError

High-level

For importlib.resources:

import pathlib
import types
from typing import ContextManager, Union
from typing.io import BinaryIO


Package = Union[str, types.ModuleType]
FileName = Union[str, os.PathLike]


def open(package: Package, file_name: FileName) -> BinaryIO:
    """Return a file-like object opened for binary-reading of the resource."""
    ...


def read(package: Package, file_name: FileName, encoding: str = "utf-8",
         errors: str = "strict") -> str:
    """Return the decoded string of the resource.

    The decoding-related arguments have the same semantics as those of
    bytes.decode().
    """
    ...


@contextlib.contextmanager
def path(package: Package, file_name: FileName) -> ContextManager[pathlib.Path]:
    """A context manager providing a file path object to the resource.

    If the resource does not already exist on its own on the file system,
    a temporary file will be created. If the file was created, the file
    will be deleted upon exiting the context manager (no exception is
    raised if the file was deleted prior to the context manager
    exiting).
    """
    ...

If package is an actual package, it is used directly. Otherwise the argument is used in calling importlib.import_module(). The found package is expected to be an actual package, otherwise TypeError is raised.

For the file_name argument, it is expected to be only a file name with no other path parts. If any parts beyond a file name are found, a ValueError will be raised. The expectation is that all data files will exist within a directory that can be imported by Python as a package.

All functions raise FileNotFoundError if the resource does not exist or cannot be found.

Open Issues

Please see the issue tracker.