Improve mpl/cartopy version parser, move to dependencies.py

Author: lukelbd

proplot/internals/dependencies.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+"""
+Utilities for handling dependencies and version changes.
+"""
+from numbers import Real
+
+# Matplotlib version
+import matplotlib
+
+from . import warnings
+
+
+class _version(list):
+    """
+    Casual parser for ``major.minor`` style version strings. We do not want to
+    add a 'packaging' dependency and only care about major and minor tags.
+    """
+    def __str__(self):
+        return self._version
+
+    def __repr__(self):
+        return f'version({self._version})'
+
+    def __init__(self, version):
+        try:
+            if isinstance(version, Real):
+                version = str(version)
+            if not isinstance(version, str):
+                version = '.'.join(version)
+            major, minor, *_ = version.split('.')
+            major, minor = int(major or 0), int(minor or 0)
+        except Exception:
+            warnings._warn_proplot(
+                f"Unexpected version {version!r}. Interpreting as '0.0'."
+            )
+            major = minor = 0
+        self._version = version
+        super().__init__([major, minor])  # then use builtin python list sorting
+
+    def __eq__(self, other):
+        return super().__eq__(_version(other))
+
+    def __ne__(self, other):
+        return super().__ne__(_version(other))
+
+    def __gt__(self, other):
+        return super().__gt__(_version(other))
+
+    def __lt__(self, other):
+        return super().__lt__(_version(other))
+
+    def __ge__(self, other):
+        return super().__ge__(_version(other))
+
+    def __le__(self, other):
+        return super().__le__(_version(other))
+
+
+_version_mpl = _version(matplotlib.__version__)
+
+# Cartopy version
+try:
+    import cartopy
+except ImportError:
+    _version_cartopy = _version('0.0')
+else:
+    _version_cartopy = _version(cartopy.__version__)