Fix: Treat Generic classes as not being is_list_like

doc/source/whatsnew/v1.5.2.rst

@@ -27,8 +27,8 @@ Fixed regressions
 Bug fixes
 ~~~~~~~~~
 - Bug in the Copy-on-Write implementation losing track of views in certain chained indexing cases (:issue:`48996`)
+- Fixed bug when instantiating a ``DataFrame`` subclass inheriting from ``typing.Generic`` that triggered a ``UserWarning`` on python 3.11 (:issue:49649)
 -
-
 .. ---------------------------------------------------------------------------
 .. _whatsnew_152.other:
 

pandas/_libs/lib.pyx

@@ -1,7 +1,10 @@
 from collections import abc
 from decimal import Decimal
 from enum import Enum
-from typing import Literal
+from typing import (
+    Literal,
+    _GenericAlias,
+)
 
 cimport cython
 from cpython.datetime cimport (
@@ -1095,7 +1098,8 @@ cdef inline bint c_is_list_like(object obj, bint allow_sets) except -1:
         # equiv: `isinstance(obj, abc.Iterable)`
         getattr(obj, "__iter__", None) is not None and not isinstance(obj, type)
         # we do not count strings/unicode/bytes as list-like
-        and not isinstance(obj, (str, bytes))
+        # exclude Generic types that have __iter__
+        and not isinstance(obj, (str, bytes, _GenericAlias))
         # exclude zero-dimensional duck-arrays, effectively scalars
         and not (hasattr(obj, "ndim") and obj.ndim == 0)
         # exclude sets if allow_sets is False

pandas/tests/dtypes/test_inference.py

@@ -18,7 +18,11 @@
 from numbers import Number
 import re
 import sys
-from typing import Iterator
+from typing import (
+    Generic,
+    Iterator,
+    TypeVar,
+)
 
 import numpy as np
 import pytest
@@ -229,6 +233,22 @@ def __getitem__(self, item):
     assert not inference.is_list_like(NotListLike())
 
 
+def test_is_list_like_generic():
+    # GH 49649
+    # is_list_like was yielding false positives for Generic classes in python 3.11
+    T = TypeVar("T")
+
+    class MyDataFrame(DataFrame, Generic[T]):
+        ...
+
+    tstc = MyDataFrame[int]
+    tst = MyDataFrame[int]({"x": [1, 2, 3]})
+
+    assert not inference.is_list_like(tstc)
+    assert isinstance(tst, DataFrame)
+    assert inference.is_list_like(tst)
+
+
 def test_is_sequence():
     is_seq = inference.is_sequence
     assert is_seq((1, 2))