Issue pandas-dev#5452 add default option to get_group

Author: kinow

pandas/core/groupby/groupby.py

@@ -659,7 +659,7 @@ def curried(x):
 
         return wrapper
 
-    def get_group(self, name, obj=None):
+    def get_group(self, name, obj=None, default=None):
         """
         Construct DataFrame from group with provided name.
 
@@ -671,6 +671,9 @@ def get_group(self, name, obj=None):
             the DataFrame to take the DataFrame out of.  If
             it is None, the object groupby was called on will
             be used
+        default : object
+            the default object in case the group requested is
+            not found
 
         Returns
         -------
@@ -681,6 +684,8 @@ def get_group(self, name, obj=None):
 
         inds = self._get_index(name)
         if not len(inds):
+            if default is not None:
+                return default
             raise KeyError(name)
 
         return obj.take(inds, axis=self.axis)

pandas/tests/groupby/test_groupby.py

@@ -1948,3 +1948,14 @@ def test_shift_bfill_ffill_tz(tz_naive_fixture, op, expected):
     result = getattr(grouped, op)()
     expected = DataFrame(expected).assign(time=lambda x: x.time.dt.tz_localize(tz))
     assert_frame_equal(result, expected)
+
+
+def test_get_group_default():
+    # Issue: 9299
+    data = DataFrame({"ind": [0, 0, 2, 2]})
+    gb = data.groupby("ind")
+
+    result = gb.get_group(1, default=gb.get_group(0))
+    expected = gb.get_group(0)
+
+    assert_frame_equal(result, expected)