Merge pull request #1408: filter: Properly check for empty metadata

nextstrain · Feb 8, 2024 · 9b31ad8 · 9b31ad8
2 parents 36d38a7 + 4e4fc33
commit 9b31ad8
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/augur/filter/subsample.py b/augur/filter/subsample.py
@@ -68,11 +68,17 @@ def get_groups_for_subsampling(strains, metadata, group_by=None):
     >>> group_by_strain = get_groups_for_subsampling(strains, metadata, group_by)
     >>> group_by_strain
     {'strain1': (2020, (2020, 1), 'unknown'), 'strain2': (2020, (2020, 2), 'unknown')}
+
+    We can group metadata without any non-ID columns.
+
+    >>> metadata = pd.DataFrame([{"strain": "strain1"}, {"strain": "strain2"}]).set_index("strain")
+    >>> get_groups_for_subsampling(strains, metadata, group_by=('_dummy',))
+    {'strain1': ('_dummy',), 'strain2': ('_dummy',)}
     """
     metadata = metadata.loc[list(strains)]
     group_by_strain = {}
 
-    if metadata.empty:
+    if len(metadata) == 0:
         return group_by_strain
 
     if not group_by or group_by == ('_dummy',):