Bugfix/get group

doc/source/whatsnew/v1.1.0.rst

@@ -309,6 +309,11 @@ Plotting
 -
 - Bug in :meth:`DataFrame.boxplot` and :meth:`DataFrame.plot.boxplot` lost color attributes of ``medianprops``, ``whiskerprops``, ``capprops`` and ``medianprops`` (:issue:`30346`)
 
+Groupby
+^^^^^^^
+
+- Bug in :meth:`GroupBy.get_group` raises ``KeyError`` when a ``name`` that does not exist is searched for (:issue:`32492`)
+
 
 Groupby/resample/rolling
 ^^^^^^^^^^^^^^^^^^^^^^^^

pandas/core/groupby/_test_get_groups.py

@@ -0,0 +1,109 @@
+# DO NOT MERGE _test_get_groups.py WITH ACTUAL PANDAS
+# DO NOT MERGE _test_get_groups.py WITH ACTUAL PANDAS
+# DO NOT MERGE _test_get_groups.py WITH ACTUAL PANDAS
+
+import unittest
+
+from pandas import DataFrame
+from pandas.testing import assert_frame_equal
+import numpy as np
+
+class _test_get_groups(unittest.TestCase):
+    def test_discovered_invalid(self):
+        df = DataFrame(data={
+            'A': ['a1', 'a2', None],
+            'B': ['b1', 'b2', 'b1'],
+            'val': [1, 2, 3],
+        })
+        grps = df.groupby(by=['A', 'B'])
+        self.assertRaises(KeyError, grps.get_group, ('a1', 'b2'))
+
+    def test_single_row_valid(self):
+        df = DataFrame(data={
+            'A': ['a1', 'a2', None],
+            'B': ['b1', 'b2', 'b1'],
+            'val': [1, 2, 3],
+        })
+        expected = DataFrame(data={
+            'A': ['a1'],
+            'B': ['b1'],
+            'val': [1,],
+        })
+        grps = df.groupby(by=['A', 'B'])
+        assert_frame_equal(grps.get_group(('a1', 'b1')), expected)
+
+    def test_alternate_invalid(self):
+        df = DataFrame(data={
+            'A': ['a1', 'a2', None],
+            'B': ['b1', 'b2', 'b1'],
+            'val': [1, 2, 3],
+        })
+        grps = df.groupby(by=['A', 'B'])
+        self.assertRaises(KeyError, grps.get_group, ('a2', 'b1'))
+
+    def test_double_row_valid(self):
+        df = DataFrame(data={
+            'A': ['a1', 'a2', None],
+            'B': ['b1', 'b2', 'b1'],
+            'val': [1, 2, 3],
+        })
+        expected = DataFrame(data={
+            'A': ['a1', None],
+            'B': ['b1', 'b1'],
+            'val': [1, 3],
+        })
+        grps = df.groupby(by=['B'])
+        self.assertEqual(True, np.array_equal(grps.get_group(('b1')).values, expected.values))
+
+    def test_expect_empty(self):
+        df = DataFrame(data={
+            'A': ['a1', 'a2', None],
+            'B': ['b1', 'b2', 'b1'],
+            'val': [1, 2, 3],
+        })
+        grps = df.groupby(by=['B'])
+        self.assertRaises(KeyError, grps.get_group, ('b3'))
+
+    def test_double_row_valid(self):
+        df = DataFrame({'Animal': ['Falcon', 'Falcon',
+                                   'Parrot', 'Parrot'],
+                        'Max Speed': [380., 370., 24., 26.],
+                        'bullshit': ['a', 'b', 'c', 'd']})
+        expected = DataFrame({'Animal': ['Falcon', 'Falcon'],
+                        'Max Speed': [380., 370.],
+                        'bullshit': ['a', 'b']})
+        grps = df.groupby(['Animal'])
+        assert_frame_equal(grps.get_group(('Falcon')), expected)
+
+    def test_multi_group_multi_result(self):
+        df = DataFrame([('bird', 'Falconiformes', 389.0),
+                        ('bird', 'Psittaciformes', 24.0),
+                        ('mammal', 'Carnivora', 80.2),
+                        ('mammal', 'Primates', None),
+                        ('mammal', 'Carnivora', 58)],
+                        index=['falcon', 'parrot', 'lion', 'monkey', 'leopard'],
+                        columns=('class', 'order', 'max_speed'))
+        expected = DataFrame([('mammal', 'Carnivora', 80.2),
+                        ('mammal', 'Carnivora', 58)],
+                        index=['lion', 'leopard'],
+                        columns=('class', 'order', 'max_speed'))
+        grps = df.groupby(['class', 'order']);
+        assert_frame_equal(grps.get_group(('mammal','Carnivora')), expected)
+
+    def test_single_group_no_tuple(self):
+        df = DataFrame([('bird', 'Falconiformes', 389.0),
+                        ('bird', 'Psittaciformes', 24.0),
+                        ('mammal', 'Carnivora', 80.2),
+                        ('mammal', 'Primates', None),
+                        ('mammal', 'Carnivora', 58)],
+                        index=['falcon', 'parrot', 'lion', 'monkey', 'leopard'],
+                        columns=('class', 'order', 'max_speed'))
+        expected = DataFrame([('bird', 'Falconiformes', 389.0),
+                        ('bird', 'Psittaciformes', 24.0)],
+                        index=['falcon', 'parrot'],
+                        columns=('class', 'order', 'max_speed'))
+        grps = df.groupby(['class']);
+        assert_frame_equal(grps.get_group('bird'), expected)
+
+if __name__ == '__main__':
+    unittest.main()

pandas/core/groupby/groupby.py

@@ -685,6 +685,25 @@ def get_group(self, name, obj=None):
         if not len(inds):
             raise KeyError(name)
 
+        try:
+            isValid = True
+            for index in inds:
+                for i in range(len(self.keys)):
+                    key = self.keys[i]
+                    # if the cell does not contain the searched for data
+                    if (type(name) != tuple):
+                        if obj.iloc[index, :][key] != name:
+                            isValid = False
+                    elif obj.iloc[index, :][key] != name[i]:
+                        isValid = False
+                    else:
+                        isValid = isValid and True
+        except TypeError:
+            pass
+        else:
+            if not isValid:
+                raise KeyError(name)
+
         return obj._take_with_is_copy(inds, axis=self.axis)
 
     def __iter__(self):