require Python >= 3.8

Numpy NEP29 dropped support for Python < 3.8 in December 2021.
We are having a harder time supporting corner cases in Python 3.7.

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     name: ${{ matrix.os }} Python ${{ matrix.python-version }}
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.8', '3.9', '3.10', '3.11']
         os: [ubuntu-latest]
         include:
         - os: macos-latest

.github/workflows/ci_stdlib_only.yml

@@ -18,7 +18,7 @@ jobs:
     name: ${{ matrix.os }} Python ${{ matrix.python-version }}
     strategy:
       matrix:
-        python-version: [ '3.7', '3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.8', '3.9', '3.10', '3.11']
         os: ['ubuntu-latest']
         include:
         - os: macos-latest

README.md

@@ -24,8 +24,8 @@ Thanks to our [contributors](./.github/contributors.md).
 
 ## Prerequisites
 
-Pymap3d is compatible with Python ≥ 3.7 including PyPy.
-Numpy and AstroPy are optional; algorithms from Vallado and Meeus are used if AstroPy is not present.
+Numpy and AstroPy are optional.
+Algorithms from Vallado and Meeus are used if AstroPy is not present.
 
 ## Install
 

pyproject.toml

@@ -14,7 +14,7 @@ classifiers = ["Development Status :: 5 - Production/Stable",
  "Programming Language :: Python :: 3",
  "Topic :: Scientific/Engineering :: GIS"
 ]
-requires-python = ">=3.7"
+requires-python = ">=3.8"
 dynamic = ["version", "readme"]
 
 [tool.setuptools.dynamic]

src/pymap3d/ellipsoid.py

@@ -3,13 +3,13 @@
 from __future__ import annotations
 from math import sqrt
 from dataclasses import dataclass, field
+from typing import TypedDict
 import sys
-from typing import Dict  # for Python < 3.9
 
-if sys.version_info >= (3, 8):
-    from typing import TypedDict
+if sys.version_info < (3, 9):
+    from typing import Dict
 else:
-    from typing_extensions import TypedDict
+    Dict = dict
 
 
 class Model(TypedDict):