ENH: little helper utility to find dicts intersection

Author: yarikoptic

heudiconv/tests/test_utils.py

@@ -5,18 +5,20 @@
 import mock
 
 from heudiconv.utils import (
-    get_known_heuristics_with_descriptions,
+    create_tree,
+    get_datetime,
+    get_dicts_intersection,
     get_heuristic_description,
-    load_heuristic,
+    get_known_heuristics_with_descriptions,
     json_dumps_pretty,
+    JSONDecodeError,
+    load_heuristic,
     load_json,
-    create_tree,
+    remove_prefix,
+    remove_suffix,
     save_json,
     update_json,
-    get_datetime,
-    remove_suffix,
-    remove_prefix,
-    JSONDecodeError)
+)
 
 import pytest
 from .utils import HEURISTICS_PATH
@@ -170,3 +172,10 @@ def test_remove_prefix():
     assert remove_prefix(s, '') == s
     assert remove_prefix(s, 'foo') == s
     assert remove_prefix(s, 'jason') == '.bourne'
+
+
+def test_get_dicts_intersection():
+    assert get_dicts_intersection([]) == {}
+    assert get_dicts_intersection([{"a": 1}]) == {"a": 1}
+    assert get_dicts_intersection([{"a": 1}, {"b": 2}]) == {}
+    assert get_dicts_intersection([{"a": 1}, {"a": 1, "b": 2}]) == {"a": 1}

heudiconv/utils.py

@@ -645,3 +645,17 @@ def remove_prefix(s, pre):
     if pre and s.startswith(pre):
         return s[len(pre):]
     return s
+
+
+def get_dicts_intersection(recs: list[dict]) -> dict:
+    """Given a list of dictionaries, return a dict of key:values which are the same
+    across all entries
+    """
+    if not recs:
+        return {}
+    common_keys = recs[0].copy()
+    for r in recs[1:]:
+        for k, v in common_keys.copy().items():
+            if k not in r or r[k] != v:
+                common_keys.pop(k)
+    return common_keys