follow-up to pandas-dev#29314

Author: jbrockmendel

pandas/_libs/algos.pyx

@@ -380,6 +380,18 @@ ctypedef fused algos_t:
 
 
 def _validate_limit(nobs: int, limit=None) -> int:
+    """
+    Check that the `limit` argument is a positive integer.
+
+    Parameters
+    ----------
+    nobs : int
+    limit : object
+
+    Returns
+    -------
+    int
+    """
     if limit is None:
         lim = nobs
     else:

pandas/core/internals/blocks.py

@@ -7,7 +7,7 @@
 
 import numpy as np
 
-from pandas._libs import NaT, lib, tslib, writers
+from pandas._libs import NaT, algos as libalgos, lib, tslib, writers
 from pandas._libs.index import convert_scalar
 import pandas._libs.internals as libinternals
 from pandas._libs.tslibs import Timedelta, conversion
@@ -393,10 +393,7 @@ def fillna(self, value, limit=None, inplace=False, downcast=None):
 
         mask = isna(self.values)
         if limit is not None:
-            if not is_integer(limit):
-                raise ValueError("Limit must be an integer")
-            if limit < 1:
-                raise ValueError("Limit must be greater than 0")
+            limit = libalgos._validate_limit(None, limit=limit)
             mask[mask.cumsum(self.ndim - 1) > limit] = False
 
         if not self._can_hold_na:

pandas/core/missing.py

@@ -11,7 +11,6 @@
     ensure_float64,
     is_datetime64_dtype,
     is_datetime64tz_dtype,
-    is_integer,
     is_integer_dtype,
     is_numeric_v_string_like,
     is_scalar,
@@ -191,13 +190,7 @@ def interpolate_1d(
             )
 
     # default limit is unlimited GH #16282
-    if limit is None:
-        # limit = len(xvalues)
-        pass
-    elif not is_integer(limit):
-        raise ValueError("Limit must be an integer")
-    elif limit < 1:
-        raise ValueError("Limit must be greater than 0")
+    limit = algos._validate_limit(nobs=None, limit=limit)
 
     from pandas import Series