Replace pkg_resources with importlib.metadata

pkg_resources is deprecated in favor of importlib.metadata (https://setuptools.readthedocs.io/en/latest/pkg_resources.html).

Due to its caching behaviour, using pkg_resources causes errors on google colab (huggingface/transformers#10964), which switching to importlib.metadata solves. For version before 3.8, the importlib-metadata package provides an official backport.

pynndescent/__init__.py

@@ -1,7 +1,14 @@
-import pkg_resources
+import sys
+
 import numba
+
 from .pynndescent_ import NNDescent, PyNNDescentTransformer
 
+if sys.version_info[:2] >= (3, 8):
+    import importlib.metadata as importlib_metadata
+else:
+    import importlib_metadata
+
 # Workaround: https://github.com/numba/numba/issues/3341
 if numba.config.THREADING_LAYER == "omp":
     try:
@@ -12,4 +19,4 @@
         # might be a missing symbol due to e.g. tbb libraries missing
         numba.config.THREADING_LAYER = "workqueue"
 
-__version__ = pkg_resources.get_distribution("pynndescent").version
+__version__ = importlib_metadata.version("pynndescent")

setup.py

@@ -42,6 +42,7 @@ def readme():
         "numba >= 0.51.2",
         "llvmlite >= 0.30",
         "joblib >= 0.11",
+        'importlib-metadata >= 4.8.1; python_version < "3.8"',
     ],
     "ext_modules": [],
     "cmdclass": {},