Fixing issue 95 (#96)

Better typing control (removed typing_extension) and dropped support for Python 3.7.

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
         shell: bash -l {0}
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10']
+        python-version: ['3.8', '3.9', '3.10']
     steps:
       - uses: actions/checkout@v2
       - uses: conda-incubator/setup-miniconda@v2

rmsd/calculate_rmsd.py

@@ -15,14 +15,13 @@
 import re
 import sys
 from pathlib import Path
-from typing import Any, Iterator, List, Optional, Set, Tuple, Union
+from typing import Any, Iterator, List, Optional, Protocol, Set, Tuple, Union
 
 import numpy as np
 from numpy import ndarray
 from scipy.optimize import linear_sum_assignment  # type: ignore
 from scipy.spatial import distance_matrix  # type: ignore
 from scipy.spatial.distance import cdist  # type: ignore
-from typing_extensions import Protocol
 
 try:
     import qml  # type: ignore

setup.py

@@ -31,7 +31,7 @@
     long_description=long_description,
     url="https://github.com/charnley/rmsd",
     license="BSD-2-Clause",
-    python_requires=">=3.6",
+    python_requires=">=3.8",
     install_requires=[
         "numpy",
         "scipy",