common/utils.py: added 'deep_update' function

Update values of nested dict of varying depth

bliss/common/utils.py

@@ -606,3 +606,19 @@ class autocomplete_property(property):
     """
 
     pass
+
+
+def deep_update(source, overrides):
+    """
+    Update a nested dictionary or similar mapping.
+    Modify ``source`` in place.
+
+    Copied from https://stackoverflow.com/questions/3232943/update-value-of-a-nested-dictionary-of-varying-depth/32357112#32357112
+    """
+    for key, value in overrides.items():
+        if isinstance(value, collections.abc.Mapping) and value:
+            returned = deep_update(source.get(key, {}), value)
+            source[key] = returned
+        else:
+            source[key] = overrides[key]
+    return source

bliss/scanning/scan.py

@@ -23,7 +23,7 @@ from bliss.common.event import connect, send, disconnect
 from bliss.common.cleanup import error_cleanup, axis as cleanup_axis, capture_exceptions
 from bliss.common.greenlet_utils import KillMask
 from bliss.common.plot import get_flint, CurvePlot, ImagePlot
-from bliss.common.utils import periodic_exec
+from bliss.common.utils import periodic_exec, deep_update
 from .scan_meta import get_user_scan_meta
 from bliss.common.utils import Statistics, Null
 from bliss.config.conductor import client
@@ -961,7 +961,7 @@ class Scan:
                 # make sure that 'positioners' entry is not updated
                 tmp_dict["instrument"].pop("positioners")
                 tmp_dict["instrument"].pop("positioners_dial")
-                nested_dict_update(self._scan_info, tmp_dict)
+                deep_update(self._scan_info, tmp_dict)
 
                 # update scan_info in redis
                 self.node._info.update(self.scan_info)
@@ -1124,24 +1124,3 @@ class Scan:
             gevent.joinall(preset_tasks, raise_error=True)
         finally:
             gevent.killall(preset_tasks)
-
-
-# there should be something like this in the python standard lib, but I didn't find it...
-# ... suggestions welcome
-# ... in case we keep our own implementation ... where should it be? in utils?
-def nested_dict_update(dict_to_update, newdict):
-    present_key_value_pairs = [
-        (key, value) for (key, value) in newdict.items() if key in dict_to_update.keys()
-    ]
-    new_key_value_pairs = [
-        (key, value)
-        for (key, value) in newdict.items()
-        if not key in dict_to_update.keys()
-    ]
-    for key, new_value in present_key_value_pairs:
-        if isinstance(new_value, dict):
-            dict_to_update[key] = nested_dict_update(dict_to_update[key], new_value)
-        else:
-            dict_to_update[key] = new_value
-    dict_to_update.update(dict(new_key_value_pairs))
-    return dict_to_update

tests/test_standard.py

@@ -7,8 +7,8 @@
 
 from bliss import setup_globals
 from bliss.common.standard import wa, wm, sta, stm
-
 from bliss.shell.cli import repl
+from bliss.common.utils import deep_update
 
 repl.ERROR_REPORT.expert_mode = True
 
@@ -168,3 +168,30 @@ def test_stm_exception(beacon, capsys):
 
     errmsg = "RuntimeError: Error on motor 'bad': BAD POSITION\n"
     assert captured.err[-len(errmsg) :] == errmsg
+
+
+def test_deep_update():
+    source = {"hello1": 1}
+    overrides = {"hello2": 2}
+    deep_update(source, overrides)
+    assert source == {"hello1": 1, "hello2": 2}
+
+    source = {"hello": "to_override"}
+    overrides = {"hello": "over"}
+    deep_update(source, overrides)
+    assert source == {"hello": "over"}
+
+    source = {"hello": {"value": "to_override", "no_change": 1}}
+    overrides = {"hello": {"value": "over"}}
+    deep_update(source, overrides)
+    assert source == {"hello": {"value": "over", "no_change": 1}}
+
+    source = {"hello": {"value": "to_override", "no_change": 1}}
+    overrides = {"hello": {"value": {}}}
+    deep_update(source, overrides)
+    assert source == {"hello": {"value": {}, "no_change": 1}}
+
+    source = {"hello": {"value": {}, "no_change": 1}}
+    overrides = {"hello": {"value": 2}}
+    deep_update(source, overrides)
+    assert source == {"hello": {"value": 2, "no_change": 1}}