From 60ab9ca8c34af7b1e72b75ee3be052f44db149b5 Mon Sep 17 00:00:00 2001
From: Eric Giguere <eric.giguere@calculquebec.ca>
Date: Fri, 16 Aug 2024 11:02:14 -0400
Subject: [PATCH 1/2] numpy_backend as a property

---
 qutip/core/numpy_backend.py |  9 +++------
 qutip/core/options.py       | 31 +++++++++++++++++++++++++------
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/qutip/core/numpy_backend.py b/qutip/core/numpy_backend.py
index bbeb247fe8..e887527e9a 100644
--- a/qutip/core/numpy_backend.py
+++ b/qutip/core/numpy_backend.py
@@ -1,14 +1,11 @@
 from ..settings import settings
 
-
 class NumpyBackend:
-    @property
-    def backend(self):
-        return settings.core["numpy_backend"]
+    def _qutip_setting_backend(self, np):
+        self.np = np
 
     def __getattr__(self, name):
-        backend = object.__getattribute__(self, 'backend')
-        return getattr(backend, name)
+        return getattr(self.np, name)
 
 
 # Initialize the numpy backend
diff --git a/qutip/core/options.py b/qutip/core/options.py
index c9f156729d..a55d79877d 100644
--- a/qutip/core/options.py
+++ b/qutip/core/options.py
@@ -1,5 +1,6 @@
 from ..settings import settings
-import numpy as np
+from .numpy_backend import np as qt_np
+import numpy
 __all__ = ["CoreOptions"]
 
 
@@ -9,8 +10,12 @@ class QutipOptions:
 
     Define basic method to wrap an ``options`` dict.
     Default options are in a class _options dict.
+
+    Options can also act as properties. The ``_properties`` map options keys to
+    a function to call when the ``QutipOptions`` become the default.
     """
     _options = {}
+    _properties = {}
     _settings_name = None  # Where the default is in settings
 
     def __init__(self, **options):
@@ -24,12 +29,17 @@ def __contains__(self, key):
         return key in self.options
 
     def __getitem__(self, key):
-        # Let the dict catch the KeyError
+        # Let the dict catch the
         return self.options[key]
 
     def __setitem__(self, key, value):
         # Let the dict catch the KeyError
         self.options[key] = value
+        if (
+            key in self._properties
+            and self is getattr(settings, self._settings_name)
+        ):
+            self._properties[key](value)
 
     def __repr__(self, full=True):
         out = [f"<{self.__class__.__name__}("]
@@ -44,10 +54,15 @@ def __repr__(self, full=True):
 
     def __enter__(self):
         self._backup = getattr(settings, self._settings_name)
-        setattr(settings, self._settings_name, self)
+        self._set_as_global_default()
 
     def __exit__(self, exc_type, exc_value, exc_traceback):
-        setattr(settings, self._settings_name, self._backup)
+        self._backup._set_as_global_default()
+
+    def _set_as_global_default(self):
+        setattr(settings, self._settings_name, self)
+        for key in self._properties:
+            self._properties[key](self.options[key])
 
 
 class CoreOptions(QutipOptions):
@@ -129,10 +144,14 @@ class CoreOptions(QutipOptions):
         # Hermiticity checks can be slow, stop jitting, etc.
         "auto_real_casting": True,
         # Default backend is numpy
-        "numpy_backend": np
+        "numpy_backend": numpy
     }
     _settings_name = "core"
+    _properties = {
+        "numpy_backend": qt_np._qutip_setting_backend,
+    }
 
 
 # Creating the instance of core options to use everywhere.
-settings.core = CoreOptions()
+# settings.core = CoreOptions()
+CoreOptions()._set_as_global_default()

From cc9808b71f314530b8b43bf3f9fcf59f942ef90c Mon Sep 17 00:00:00 2001
From: Eric Giguere <eric.giguere@calculquebec.ca>
Date: Fri, 16 Aug 2024 11:17:58 -0400
Subject: [PATCH 2/2] change attribute names

---
 qutip/core/numpy_backend.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/qutip/core/numpy_backend.py b/qutip/core/numpy_backend.py
index e887527e9a..39fa1d0947 100644
--- a/qutip/core/numpy_backend.py
+++ b/qutip/core/numpy_backend.py
@@ -1,11 +1,12 @@
 from ..settings import settings
 
+
 class NumpyBackend:
     def _qutip_setting_backend(self, np):
-        self.np = np
+        self._qt_np = np
 
     def __getattr__(self, name):
-        return getattr(self.np, name)
+        return getattr(self._qt_np, name)
 
 
 # Initialize the numpy backend