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100 lines
2.7 KiB
100 lines
2.7 KiB
from __future__ import annotations
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import warnings
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from typing import Any, Dict, Iterable, Optional
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__all__ = ["lazy_import"]
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def import_name(name: str, source: str, namespace: Dict[str, Any]) -> Any:
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"""
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Import ``name`` from ``source`` in ``namespace``.
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There are two use cases:
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- ``name`` is an object defined in ``source``;
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- ``name`` is a submodule of ``source``.
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Neither :func:`__import__` nor :func:`~importlib.import_module` does
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exactly this. :func:`__import__` is closer to the intended behavior.
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"""
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level = 0
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while source[level] == ".":
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level += 1
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assert level < len(source), "importing from parent isn't supported"
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module = __import__(source[level:], namespace, None, [name], level)
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return getattr(module, name)
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def lazy_import(
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namespace: Dict[str, Any],
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aliases: Optional[Dict[str, str]] = None,
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deprecated_aliases: Optional[Dict[str, str]] = None,
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) -> None:
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"""
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Provide lazy, module-level imports.
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Typical use::
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__getattr__, __dir__ = lazy_import(
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globals(),
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aliases={
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"<name>": "<source module>",
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...
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},
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deprecated_aliases={
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...,
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}
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)
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This function defines ``__getattr__`` and ``__dir__`` per :pep:`562`.
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"""
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if aliases is None:
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aliases = {}
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if deprecated_aliases is None:
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deprecated_aliases = {}
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namespace_set = set(namespace)
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aliases_set = set(aliases)
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deprecated_aliases_set = set(deprecated_aliases)
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assert not namespace_set & aliases_set, "namespace conflict"
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assert not namespace_set & deprecated_aliases_set, "namespace conflict"
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assert not aliases_set & deprecated_aliases_set, "namespace conflict"
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package = namespace["__name__"]
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def __getattr__(name: str) -> Any:
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assert aliases is not None # mypy cannot figure this out
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try:
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source = aliases[name]
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except KeyError:
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pass
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else:
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return import_name(name, source, namespace)
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assert deprecated_aliases is not None # mypy cannot figure this out
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try:
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source = deprecated_aliases[name]
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except KeyError:
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pass
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else:
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warnings.warn(
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f"{package}.{name} is deprecated",
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DeprecationWarning,
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stacklevel=2,
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)
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return import_name(name, source, namespace)
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raise AttributeError(f"module {package!r} has no attribute {name!r}")
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namespace["__getattr__"] = __getattr__
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def __dir__() -> Iterable[str]:
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return sorted(namespace_set | aliases_set | deprecated_aliases_set)
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namespace["__dir__"] = __dir__
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