Use setuptools_scm

Follows up ufoym#47

- on [pypi](https://pypi.org/project/torchsampler/0.1.1/) it's 0.1.1
- on github it's [0.1.0](https://github.com/ufoym/imbalanced-dataset-sampler/releases/tag/v0.1.0)
    - but the attached [wheel](https://github.com/ufoym/imbalanced-dataset-sampler/releases/download/v0.1.0/torchsampler-0.1.1-py3-none-any.whl)
      and [sdist](https://github.com/ufoym/imbalanced-dataset-sampler/releases/download/v0.1.0/torchsampler-0.1.1.tar.gz) are 0.1.1

[`setuptools-scm`](https://pypi.org/project/setuptools-scm/) makes git the single-source of truth
for the version of the package, and works well with the build script in ufoym#47 (which is triggered
by tagging a new version in git).

.github/workflows/code-format.yml

@@ -48,7 +48,10 @@ jobs:
       - name: Install dependencies
         run: |
           pip install --upgrade pip
-          pip install yapf
+          # TODO: in the next version of yapf you can use the clearer
+          #       pip install yapf[pyproject]
+          #       see ttps://github.com/google/yapf/pull/964
+          pip install yapf toml
           pip list
         shell: bash
       - name: yapf

.pre-commit-config.yaml

@@ -28,6 +28,8 @@ repos:
     rev: v0.32.0
     hooks:
       - id: yapf
+        # needed for pyproject.toml: https://github.com/pre-commit/mirrors-yapf/issues/15#issuecomment-814037905
+        additional_dependencies: [toml]
         name: formatting
 
   - repo: https://github.com/PyCQA/flake8

pyproject.toml

@@ -0,0 +1,2 @@
+[build-system]
+requires = ["setuptools>=45", "wheel", "setuptools_scm>=6.2"]

requirements.txt

@@ -1,3 +1,4 @@
 torch>=1.3
 torchvision>=0.5
 pandas
+importlib_metadata; python_version<'3.8'

setup.py

@@ -20,7 +20,7 @@
 
 setup(
     name='torchsampler',
-    version=about.__version__,
+    use_scm_version=True,
     url=about.__homepage__,
     author=about.__author__,
     author_email=about.__author_email__,
@@ -30,6 +30,7 @@
     long_description_content_type='text/markdown',
     packages=['torchsampler'],
     keywords='sampler,pytorch,dataloader',
+    setup_requires=['setuptools_scm'],
     install_requires=requirements,
     python_requires='>=3.6',
     include_package_data=True,

torchsampler/__about__.py

@@ -1,3 +1,9 @@
+from importlib.metadata import version, PackageNotFoundError
+try:
+    __version__ = version("torchsampler")
+except PackageNotFoundError:
+    # package is not installed (i.e. we're probably in the build process itself)
+    pass
 __version__ = "0.1.1"
 __author__ = "Ming, et al."
 __author_email__ = "a@ufoym.com"