BUG: Avoid exceptions in is_dtype

Author: TomAugspurger

pandas/core/dtypes/base.py

@@ -2,6 +2,7 @@
 import numpy as np
 
 from pandas import compat
+from pandas.core.dtypes.generic import ABCSeries, ABCIndexClass, ABCDataFrame
 from pandas.errors import AbstractMethodError
 
 
@@ -83,7 +84,12 @@ def is_dtype(cls, dtype):
         """
         dtype = getattr(dtype, 'dtype', dtype)
 
-        if isinstance(dtype, np.dtype):
+        if isinstance(dtype, (ABCSeries, ABCIndexClass,
+                              ABCDataFrame, np.dtype)):
+            # https://github.com/pandas-dev/pandas/issues/22960
+            # avoid passing data to `construct_from_string`. This could
+            # cause a FutureWarning from numpy about failing elementwise
+            # comparison from, e.g., comparing DataFrame == 'category'.
             return False
         elif dtype is None:
             return False

pandas/tests/dtypes/test_dtypes.py

@@ -815,3 +815,23 @@ def test_registry_find(dtype, expected):
      ('datetime64[ns, US/Eastern]', DatetimeTZDtype('ns', 'US/Eastern'))])
 def test_pandas_registry_find(dtype, expected):
     assert _pandas_registry.find(dtype) == expected
+
+
+@pytest.mark.parametrize("check", [
+    is_categorical_dtype,
+    is_datetime64tz_dtype,
+    is_period_dtype,
+    is_datetime64_ns_dtype,
+    is_datetime64_dtype,
+    is_interval_dtype,
+    is_datetime64_any_dtype,
+    is_string_dtype,
+    is_bool_dtype,
+])
+def test_is_dtype_no_warning(check):
+    data = pd.DataFrame({"A": [1, 2]})
+    with tm.assert_produces_warning(None):
+        check(data)
+
+    with tm.assert_produces_warning(None):
+        check(data["A"])