WIP: Namespaced AppContext

petsctools/__init__.py

@@ -10,6 +10,7 @@
 from .exceptions import PetscToolsException  # noqa: F401
 from .options import flatten_parameters  # noqa: F401
 from .utils import PETSC4PY_INSTALLED
+from .appctx import AppContext
 
 # Now conditionally import the functions that depend on petsc4py. If petsc4py
 # is not available then attempting to access these attributes will raise an

petsctools/appctx.py

@@ -0,0 +1,28 @@
+import itertools
+
+
+class AppContext:
+    def __init__(self):
+        self._count = itertools.count()
+        self._data = {}
+        self._missing_key = next(self._count)
+
+    @property
+    def missing_key(self):
+        return self._missing_key
+
+    def insert(self, val):
+        key = next(self._count)
+        self._data[key] = val
+        return key
+
+    def __getitem__(self, key):
+        return self._data[key]
+
+    def get(self, key, default=None):
+        if key == self.missing_key:
+            return default
+        return self._data.get(key, default=default)
+
+    def values(self):
+        return self._data.values()