Added validation check to Series.diff,updated testcase and whatsnew

doc/source/whatsnew/v2.3.0.rst

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

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,
@@ -3103,6 +3104,9 @@ 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/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()