[BUG]: Fix regression in read_table with delim_whitespace=True

doc/source/whatsnew/v1.1.3.rst

@@ -36,6 +36,7 @@ Fixed regressions
 - Fixed regression in :meth:`read_excel` with ``engine="odf"`` caused ``UnboundLocalError`` in some cases where cells had nested child nodes (:issue:`36122`,:issue:`35802`)
 - Fixed regression in :class:`DataFrame` and :class:`Series` comparisons between numeric arrays and strings (:issue:`35700`,:issue:`36377`)
 - Fixed regression when setting empty :class:`DataFrame` column to a :class:`Series` in preserving name of index in frame (:issue:`36527`)
+- Fixed regression in :meth:`read_table()` raised ``ValueError`` when ``delim_whitespace`` was set to ``True`` (:issue:`35958`)
 
 .. ---------------------------------------------------------------------------
 

pandas/io/parsers.py

@@ -757,6 +757,8 @@ def read_table(
     memory_map=False,
     float_precision=None,
 ):
+    if delim_whitespace:
+        sep = ","
     return read_csv(**locals())
 
 

pandas/tests/io/parser/test_common.py

@@ -2200,3 +2200,12 @@ def test_read_csv_with_use_inf_as_na(all_parsers):
         result = parser.read_csv(StringIO(data), header=None)
     expected = DataFrame([1.0, np.nan, 3.0])
     tm.assert_frame_equal(result, expected)
+
+
+def test_read_table_delim_whitespace_default_sep(all_parsers):
+    # GH: 35958
+    f = StringIO("a  b  c\n1 -2 -3\n4  5   6")
+    parser = all_parsers
+    result = parser.read_table(f, delim_whitespace=True)
+    expected = DataFrame({"a": [1, 4], "b": [-2, 5], "c": [-3, 6]})
+    tm.assert_frame_equal(result, expected)