208 lines
7.4 KiB
Plaintext
208 lines
7.4 KiB
Plaintext
Metadata-Version: 2.1
|
|
Name: lazy_loader
|
|
Version: 0.4
|
|
Summary: Makes it easy to load subpackages and functions on demand.
|
|
Author: Scientific Python Developers
|
|
License: BSD 3-Clause License
|
|
|
|
Copyright (c) 2022--2023, Scientific Python project
|
|
All rights reserved.
|
|
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions are met:
|
|
|
|
1. Redistributions of source code must retain the above copyright notice, this
|
|
list of conditions and the following disclaimer.
|
|
|
|
2. Redistributions in binary form must reproduce the above copyright notice,
|
|
this list of conditions and the following disclaimer in the documentation
|
|
and/or other materials provided with the distribution.
|
|
|
|
3. Neither the name of the copyright holder nor the names of its
|
|
contributors may be used to endorse or promote products derived from
|
|
this software without specific prior written permission.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
|
|
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
|
|
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
|
|
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
Project-URL: Home, https://scientific-python.org/specs/spec-0001/
|
|
Project-URL: Source, https://github.com/scientific-python/lazy_loader
|
|
Classifier: Development Status :: 4 - Beta
|
|
Classifier: License :: OSI Approved :: BSD License
|
|
Classifier: Programming Language :: Python :: 3
|
|
Classifier: Programming Language :: Python :: 3.7
|
|
Classifier: Programming Language :: Python :: 3.8
|
|
Classifier: Programming Language :: Python :: 3.9
|
|
Classifier: Programming Language :: Python :: 3.10
|
|
Classifier: Programming Language :: Python :: 3.11
|
|
Classifier: Programming Language :: Python :: 3.12
|
|
Requires-Python: >=3.7
|
|
Description-Content-Type: text/markdown
|
|
License-File: LICENSE.md
|
|
Requires-Dist: packaging
|
|
Requires-Dist: importlib-metadata ; python_version < "3.8"
|
|
Provides-Extra: dev
|
|
Requires-Dist: changelist ==0.5 ; extra == 'dev'
|
|
Provides-Extra: lint
|
|
Requires-Dist: pre-commit ==3.7.0 ; extra == 'lint'
|
|
Provides-Extra: test
|
|
Requires-Dist: pytest >=7.4 ; extra == 'test'
|
|
Requires-Dist: pytest-cov >=4.1 ; extra == 'test'
|
|
|
|
[](https://pypi.org/project/lazy_loader/)
|
|
[](https://github.com/scientific-python/lazy_loader/actions?query=workflow%3A%22test%22)
|
|
[](https://app.codecov.io/gh/scientific-python/lazy_loader/branch/main)
|
|
|
|
`lazy_loader` makes it easy to load subpackages and functions on demand.
|
|
|
|
## Motivation
|
|
|
|
1. Allow subpackages to be made visible to users without incurring import costs.
|
|
2. Allow external libraries to be imported only when used, improving import times.
|
|
|
|
For a more detailed discussion, see [the SPEC](https://scientific-python.org/specs/spec-0001/).
|
|
|
|
## Installation
|
|
|
|
```
|
|
pip install -U lazy_loader
|
|
```
|
|
|
|
We recommend using `lazy_loader` with Python >= 3.11.
|
|
If using Python 3.11, please upgrade to 3.11.9 or later.
|
|
If using Python 3.12, please upgrade to 3.12.3 or later.
|
|
These versions [avoid](https://github.com/python/cpython/pull/114781) a [known race condition](https://github.com/python/cpython/issues/114763).
|
|
|
|
## Usage
|
|
|
|
### Lazily load subpackages
|
|
|
|
Consider the `__init__.py` from [scikit-image](https://scikit-image.org):
|
|
|
|
```python
|
|
subpackages = [
|
|
...,
|
|
'filters',
|
|
...
|
|
]
|
|
|
|
import lazy_loader as lazy
|
|
__getattr__, __dir__, _ = lazy.attach(__name__, subpackages)
|
|
```
|
|
|
|
You can now do:
|
|
|
|
```python
|
|
import skimage as ski
|
|
ski.filters.gaussian(...)
|
|
```
|
|
|
|
The `filters` subpackages will only be loaded once accessed.
|
|
|
|
### Lazily load subpackages and functions
|
|
|
|
Consider `skimage/filters/__init__.py`:
|
|
|
|
```python
|
|
from ..util import lazy
|
|
|
|
__getattr__, __dir__, __all__ = lazy.attach(
|
|
__name__,
|
|
submodules=['rank'],
|
|
submod_attrs={
|
|
'_gaussian': ['gaussian', 'difference_of_gaussians'],
|
|
'edges': ['sobel', 'scharr', 'prewitt', 'roberts',
|
|
'laplace', 'farid']
|
|
}
|
|
)
|
|
```
|
|
|
|
The above is equivalent to:
|
|
|
|
```python
|
|
from . import rank
|
|
from ._gaussian import gaussian, difference_of_gaussians
|
|
from .edges import (sobel, scharr, prewitt, roberts,
|
|
laplace, farid)
|
|
```
|
|
|
|
Except that all subpackages (such as `rank`) and functions (such as `sobel`) are loaded upon access.
|
|
|
|
### Type checkers
|
|
|
|
Static type checkers and IDEs cannot infer type information from
|
|
lazily loaded imports. As a workaround you can load [type
|
|
stubs](https://mypy.readthedocs.io/en/stable/stubs.html) (`.pyi`
|
|
files) with `lazy.attach_stub`:
|
|
|
|
```python
|
|
import lazy_loader as lazy
|
|
__getattr__, __dir__, _ = lazy.attach_stub(__name__, "subpackages.pyi")
|
|
```
|
|
|
|
Note that, since imports are now defined in `.pyi` files, those
|
|
are not only necessary for type checking but also at runtime.
|
|
|
|
The SPEC [describes this workaround in more
|
|
detail](https://scientific-python.org/specs/spec-0001/#type-checkers).
|
|
|
|
### Early failure
|
|
|
|
With lazy loading, missing imports no longer fail upon loading the
|
|
library. During development and testing, you can set the `EAGER_IMPORT`
|
|
environment variable to disable lazy loading.
|
|
|
|
### External libraries
|
|
|
|
The `lazy.attach` function discussed above is used to set up package
|
|
internal imports.
|
|
|
|
Use `lazy.load` to lazily import external libraries:
|
|
|
|
```python
|
|
sp = lazy.load('scipy') # `sp` will only be loaded when accessed
|
|
sp.linalg.norm(...)
|
|
```
|
|
|
|
_Note that lazily importing *sub*packages,
|
|
i.e. `load('scipy.linalg')` will cause the package containing the
|
|
subpackage to be imported immediately; thus, this usage is
|
|
discouraged._
|
|
|
|
You can ask `lazy.load` to raise import errors as soon as it is called:
|
|
|
|
```python
|
|
linalg = lazy.load('scipy.linalg', error_on_import=True)
|
|
```
|
|
|
|
#### Optional requirements
|
|
|
|
One use for lazy loading is for loading optional dependencies, with
|
|
`ImportErrors` only arising when optional functionality is accessed. If optional
|
|
functionality depends on a specific version, a version requirement can
|
|
be set:
|
|
|
|
```python
|
|
np = lazy.load("numpy", require="numpy >=1.24")
|
|
```
|
|
|
|
In this case, if `numpy` is installed, but the version is less than 1.24,
|
|
the `np` module returned will raise an error on attribute access. Using
|
|
this feature is not all-or-nothing: One module may rely on one version of
|
|
numpy, while another module may not set any requirement.
|
|
|
|
_Note that the requirement must use the package [distribution name][] instead
|
|
of the module [import name][]. For example, the `pyyaml` distribution provides
|
|
the `yaml` module for import._
|
|
|
|
[distribution name]: https://packaging.python.org/en/latest/glossary/#term-Distribution-Package
|
|
[import name]: https://packaging.python.org/en/latest/glossary/#term-Import-Package
|