feat(index): append

Author: cmp0xff

pandas-stubs/core/indexes/base.pyi

@@ -401,7 +401,12 @@ class Index(IndexOpsMixin[S1]):
     ) -> Self: ...
     @overload
     def __getitem__(self, idx: int | tuple[np_ndarray_anyint, ...]) -> S1: ...
-    def append(self, other): ...
+    @overload
+    def append(self, other: Index[Never]) -> Index: ...
+    @overload
+    def append(self, other: Index[S1] | Sequence[Index[S1]]) -> Index[S1]: ...
+    @overload
+    def append(self, other: Index | Sequence) -> Index: ...
     def putmask(self, mask, value): ...
     def equals(self, other) -> bool: ...
     @final

pyproject.toml

@@ -39,7 +39,7 @@ mypy = "1.17.0"
 pandas = "2.3.0"
 pyarrow = ">=10.0.1"
 pytest = ">=7.1.2"
-pyright = ">=1.1.400"
+pyright = ">=1.1.403"
 ty = "^0.0.1a8"
 pyrefly = "^0.21.0"
 poethepoet = ">=0.16.5"

tests/test_indexes.py

@@ -1028,6 +1028,49 @@ def test_getitem() -> None:
     check(assert_type(i0[[0, 2]], "pd.Index[str]"), pd.Index, str)
 
 
+def test_append_any() -> None:
+    """Test pd.Index.append that gives pd.Index[Any]"""
+    first = pd.Index([1])
+    second = pd.Index(["a"])
+    third = pd.Index([1, "a"])
+    check(assert_type(first.append(second), pd.Index), pd.Index)
+    check(assert_type(first.append([second]), pd.Index), pd.Index)
+
+    check(assert_type(first.append(third), pd.Index), pd.Index)
+    check(assert_type(first.append([third]), pd.Index), pd.Index)
+    check(assert_type(first.append([second, third]), pd.Index), pd.Index)
+
+    check(assert_type(third.append([]), "pd.Index[str | int]"), pd.Index)  # type: ignore[assert-type]
+    check(assert_type(third.append([first]), pd.Index), pd.Index)
+
+
+def test_append_int() -> None:
+    """Test pd.Index[int].append"""
+    first = pd.Index([1])
+    second = pd.Index([2])
+    check(assert_type(first.append([]), "pd.Index[int]"), pd.Index, np.int64)
+    check(assert_type(first.append(second), "pd.Index[int]"), pd.Index, np.int64)
+    check(assert_type(first.append([second]), "pd.Index[int]"), pd.Index, np.int64)
+
+
+def test_append_str() -> None:
+    """Test pd.Index[str].append"""
+    first = pd.Index(["str"])
+    second = pd.Index(["rts"])
+    check(assert_type(first.append([]), "pd.Index[str]"), pd.Index, str)
+    check(assert_type(first.append(second), "pd.Index[str]"), pd.Index, str)
+    check(assert_type(first.append([second]), "pd.Index[str]"), pd.Index, str)
+
+
+def test_append_list_str() -> None:
+    """Test pd.Index[list[str]].append"""
+    first = pd.Index([["str", "rts"]])
+    second = pd.Index([["srt", "trs"]])
+    check(assert_type(first.append([]), "pd.Index[list[str]]"), pd.Index, list)
+    check(assert_type(first.append(second), "pd.Index[list[str]]"), pd.Index, list)
+    check(assert_type(first.append([second]), "pd.Index[list[str]]"), pd.Index, list)
+
+
 def test_range_index_range() -> None:
     """Test that pd.RangeIndex can be initialized from range."""
     iri = pd.RangeIndex(range(5))