Pandas BUG: AttributeError in pandas.core.algorithms.diff when passing non-numeric types

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Reproducible Example

import pandas as pd
pd.Series([1, 2, 3]).diff("hello")


Raises:

AttributeError: 'str' object has no attribute 'is_integer'

Issue Description

When passing non-numeric types (like strings, None, or other objects) to the diff function in pandas/core/algorithms.py, it raises an AttributeError instead of the expected ValueError. This affects any code that uses Series.diff(), DataFrame.diff(), or calls the diff function directly.

The issue occurs because the validation logic tries to call n.is_integer() on non-float objects that don't have this method, resulting in an AttributeError.

Expected Behavior

import pandas as pd
pd.Series([1, 2, 3]).diff("hello")

Should raise:

ValueError: periods must be an integer

Installed Versions

python : 3.12.10 OS : Linux OS-release : 4.18.0-553.56.1.el8_10.x86_64

Comment From: mroeschke

Thanks I don't see this error on main

In [1]: import pandas as pd
   ...: pd.Series([1, 2, 3]).diff("hello")

File ~/pandas/core/series.py:2837, in Series.diff(self, periods)
   2835 if not lib.is_integer(periods):
   2836     if not (is_float(periods) and periods.is_integer()):
-> 2837         raise ValueError("periods must be an integer")
   2838 result = algorithms.diff(self._values, periods)
   2839 return self._constructor(result, index=self.index, copy=False).__finalize__(
   2840     self, method="diff"
   2841 )

ValueError: periods must be an integer

so closing this PR