Moved to new test module for apply mutation (pandas-dev#33468)

Author: WillAyd

pandas/tests/groupby/test_apply_mutate.py

@@ -0,0 +1,70 @@
+import numpy as np
+
+import pandas as pd
+import pandas._testing as tm
+
+
+def test_mutate_groups():
+
+    # GH3380
+
+    df = pd.DataFrame(
+        {
+            "cat1": ["a"] * 8 + ["b"] * 6,
+            "cat2": ["c"] * 2
+            + ["d"] * 2
+            + ["e"] * 2
+            + ["f"] * 2
+            + ["c"] * 2
+            + ["d"] * 2
+            + ["e"] * 2,
+            "cat3": [f"g{x}" for x in range(1, 15)],
+            "val": np.random.randint(100, size=14),
+        }
+    )
+
+    def f_copy(x):
+        x = x.copy()
+        x["rank"] = x.val.rank(method="min")
+        return x.groupby("cat2")["rank"].min()
+
+    def f_no_copy(x):
+        x["rank"] = x.val.rank(method="min")
+        return x.groupby("cat2")["rank"].min()
+
+    grpby_copy = df.groupby("cat1").apply(f_copy)
+    grpby_no_copy = df.groupby("cat1").apply(f_no_copy)
+    tm.assert_series_equal(grpby_copy, grpby_no_copy)
+
+
+def test_no_mutate_but_looks_like():
+
+    # GH 8467
+    # first show's mutation indicator
+    # second does not, but should yield the same results
+    df = pd.DataFrame({"key": [1, 1, 1, 2, 2, 2, 3, 3, 3], "value": range(9)})
+
+    result1 = df.groupby("key", group_keys=True).apply(lambda x: x[:].key)
+    result2 = df.groupby("key", group_keys=True).apply(lambda x: x.key)
+    tm.assert_series_equal(result1, result2)
+
+
+def test_apply_function_with_indexing():
+    # GH: 33058
+    df = pd.DataFrame(
+        {"col1": ["A", "A", "A", "B", "B", "B"], "col2": [1, 2, 3, 4, 5, 6]}
+    )
+
+    def fn(x):
+        x.col2[x.index[-1]] = 0
+        return x.col2
+
+    result = df.groupby(["col1"], as_index=False).apply(fn)
+    expected = pd.Series(
+        [1, 2, 0, 4, 5, 0],
+        index=pd.MultiIndex.from_tuples(
+            [(0, 0), (0, 1), (0, 2), (1, 3), (1, 4), (1, 5)]
+        ),
+        name="col2",
+    )
+    tm.assert_series_equal(result, expected)

pandas/tests/groupby/test_groupby.py

@@ -921,51 +921,6 @@ def test_groupby_complex():
     tm.assert_series_equal(result, expected)
 
 
-def test_mutate_groups():
-
-    # GH3380
-
-    df = DataFrame(
-        {
-            "cat1": ["a"] * 8 + ["b"] * 6,
-            "cat2": ["c"] * 2
-            + ["d"] * 2
-            + ["e"] * 2
-            + ["f"] * 2
-            + ["c"] * 2
-            + ["d"] * 2
-            + ["e"] * 2,
-            "cat3": [f"g{x}" for x in range(1, 15)],
-            "val": np.random.randint(100, size=14),
-        }
-    )
-
-    def f_copy(x):
-        x = x.copy()
-        x["rank"] = x.val.rank(method="min")
-        return x.groupby("cat2")["rank"].min()
-
-    def f_no_copy(x):
-        x["rank"] = x.val.rank(method="min")
-        return x.groupby("cat2")["rank"].min()
-
-    grpby_copy = df.groupby("cat1").apply(f_copy)
-    grpby_no_copy = df.groupby("cat1").apply(f_no_copy)
-    tm.assert_series_equal(grpby_copy, grpby_no_copy)
-
-
-def test_no_mutate_but_looks_like():
-
-    # GH 8467
-    # first show's mutation indicator
-    # second does not, but should yield the same results
-    df = DataFrame({"key": [1, 1, 1, 2, 2, 2, 3, 3, 3], "value": range(9)})
-
-    result1 = df.groupby("key", group_keys=True).apply(lambda x: x[:].key)
-    result2 = df.groupby("key", group_keys=True).apply(lambda x: x.key)
-    tm.assert_series_equal(result1, result2)
-
-
 def test_groupby_series_indexed_differently():
     s1 = Series(
         [5.0, -9.0, 4.0, 100.0, -5.0, 55.0, 6.7],