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