Fix for #56716: Use assert_produces_warning instead of pytest.raises to show FutureWarning

doc/source/whatsnew/v2.3.0.rst

@@ -108,6 +108,7 @@ Performance improvements
 
 Bug fixes
 ~~~~~~~~~
+Fixed bug in :meth:`Series.diff` and :meth:`algorithms.diff` for no arg validation unlike :meth:`Dataframe.diff` for periods. (:issue:`56607`)
 
 Categorical
 ^^^^^^^^^^^

pandas/core/algorithms.py

@@ -47,6 +47,7 @@
     is_complex_dtype,
     is_dict_like,
     is_extension_array_dtype,
+    is_float,
     is_float_dtype,
     is_integer,
     is_integer_dtype,
@@ -1361,7 +1362,12 @@ def diff(arr, n: int, axis: AxisInt = 0):
     shifted
     """
 
-    n = int(n)
+    # added a check on the integer value of period
+    # see https://github.com/pandas-dev/pandas/issues/56607
+    if not lib.is_integer(n):
+        if not (is_float(n) and n.is_integer()):
+            raise ValueError("periods must be an integer")
+        n = int(n)
     na = np.nan
     dtype = arr.dtype
 

pandas/core/series.py

@@ -72,6 +72,7 @@
 )
 from pandas.core.dtypes.common import (
     is_dict_like,
+    is_float,
     is_integer,
     is_iterator,
     is_list_like,
@@ -3102,6 +3103,9 @@ def diff(self, periods: int = 1) -> Series:
         --------
         {examples}
         """
+        if not lib.is_integer(periods):
+            if not (is_float(periods) and periods.is_integer()):
+                raise ValueError("periods must be an integer")
         result = algorithms.diff(self._values, periods)
         return self._constructor(result, index=self.index, copy=False).__finalize__(
             self, method="diff"

pandas/tests/io/xml/test_xml.py

@@ -497,10 +497,9 @@ def test_wrong_file_path(parser):
     )
     filename = os.path.join("data", "html", "books.xml")
 
-    with pytest.raises(
-        FutureWarning,
-        match=msg,
-    ):
+    with tm.assert_produces_warning(
+            FutureWarning,
+            match=msg):
         read_xml(filename, parser=parser)
 
 
@@ -1369,7 +1368,8 @@ def test_empty_stylesheet(val):
     )
     kml = os.path.join("data", "xml", "cta_rail_lines.kml")
 
-    with pytest.raises(FutureWarning, match=msg):
+    # 56716: Use assert_produces_warning instead of pytest.raises to show FutureWarning
+    with tm.assert_produces_warning(FutureWarning, match=msg):
         read_xml(kml, stylesheet=val)
 
 

pandas/tests/series/methods/test_diff.py

@@ -10,6 +10,11 @@
 
 
 class TestSeriesDiff:
+    def test_diff_series_requires_integer(self):
+        series = Series(np.random.default_rng(2).standard_normal(2))
+        with pytest.raises(ValueError, match="periods must be an integer"):
+            series.diff(1.5)
+
     def test_diff_np(self):
         # TODO(__array_function__): could make np.diff return a Series
         #  matching ser.diff()