BUG: date_range not excluding dates correctly with periods and inclusive not 'both'

doc/source/whatsnew/v1.5.0.rst

@@ -473,6 +473,7 @@ Datetimelike
 - Bug in :meth:`Index.astype` when casting from object dtype to ``timedelta64[ns]`` dtype incorrectly casting ``np.datetime64("NaT")`` values to ``np.timedelta64("NaT")`` instead of raising (:issue:`45722`)
 - Bug in :meth:`SeriesGroupBy.value_counts` index when passing categorical column (:issue:`44324`)
 - Bug in :meth:`DatetimeIndex.tz_localize` localizing to UTC failing to make a copy of the underlying data (:issue:`46460`)
+- Bug in :meth:`date_range` when ``start`` or ``end`` was not specified, failed to exclude first or last date despite ``inclusive`` not being ``"both"`` (:issue:`46331`)
 -
 
 Timedelta

pandas/core/arrays/datetimes.py

@@ -484,17 +484,21 @@ def _generate_range(
                 #  to overflow and cast to e.g. f8, but if it does we need to cast
                 i8values = i8values.astype("i8")
 
+        # Apply `inclusive` rules
         if start == end:
+            # Particular case where we act iff `inclusive="neither"`
+            # cf. GH #43394
             if not left_inclusive and not right_inclusive:
                 i8values = i8values[1:-1]
-        else:
+        elif len(i8values):
             start_i8 = Timestamp(start).value
             end_i8 = Timestamp(end).value
-            if not left_inclusive or not right_inclusive:
-                if not left_inclusive and len(i8values) and i8values[0] == start_i8:
-                    i8values = i8values[1:]
-                if not right_inclusive and len(i8values) and i8values[-1] == end_i8:
-                    i8values = i8values[:-1]
+            _left, _right = None, None
+            if not left_inclusive and (i8values[0] == start_i8 or start is None):
+                _left = 1
+            if not right_inclusive and (i8values[-1] == end_i8 or end is None):
+                _right = -1
+            i8values = i8values[_left:_right]
 
         dt64_values = i8values.view("datetime64[ns]")
         dtype = tz_to_dtype(tz)

pandas/tests/indexes/datetimes/test_date_range.py

@@ -783,6 +783,34 @@ def test_range_where_start_equal_end(self, inclusive_endpoints_fixture):
 
         tm.assert_index_equal(result, expected)
 
+    def test_range_without_start_inclusive(self, inclusive_endpoints_fixture):
+        # GH 46331
+        start = Timestamp("2000-01-01")
+        end = Timestamp("2000-01-04")
+        both_range = date_range(start, end, inclusive="both")
+
+        result = date_range(end=end, periods=4, inclusive=inclusive_endpoints_fixture)
+        expected = _get_expected_range(
+            start, end, both_range, inclusive_endpoints_fixture
+        )
+
+        tm.assert_index_equal(result, expected)
+
+    def test_range_without_end_inclusive(self, inclusive_endpoints_fixture):
+        # GH 46331
+        start = Timestamp("2000-01-01")
+        end = Timestamp("2000-01-04")
+        both_range = date_range(start, end, inclusive="both")
+
+        result = date_range(
+            start=start, periods=4, inclusive=inclusive_endpoints_fixture
+        )
+        expected = _get_expected_range(
+            start, end, both_range, inclusive_endpoints_fixture
+        )
+
+        tm.assert_index_equal(result, expected)
+
 
 class TestDateRangeTZ:
     """Tests for date_range with timezones"""