BUG: Don't multiply sets during construction

doc/source/whatsnew/v1.1.0.rst

@@ -352,6 +352,7 @@ Other
   instead of ``TypeError: Can only append a Series if ignore_index=True or if the Series has a name`` (:issue:`30871`)
 - Set operations on an object-dtype :class:`Index` now always return object-dtype results (:issue:`31401`)
 - Bug in :meth:`AbstractHolidayCalendar.holidays` when no rules were defined (:issue:`31415`)
+- Bug in :class:`DataFrame` expanding sets when passed to the constructor (:issue:`32582`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/construction.py

@@ -434,7 +434,9 @@ def sanitize_array(
             subarr = subarr.copy()
         return subarr
 
-    elif isinstance(data, (list, tuple)) and len(data) > 0:
+    elif isinstance(data, (list, tuple, set)) and len(data) > 0:
+        if isinstance(data, set):
+            data = list(data)
         if dtype is not None:
             subarr = _try_cast(data, dtype, copy, raise_cast_failure)
         else:

pandas/tests/frame/test_constructors.py

@@ -2609,3 +2609,10 @@ def test_from_2d_ndarray_with_dtype(self):
 
         expected = pd.DataFrame(array_dim2).astype("datetime64[ns, UTC]")
         tm.assert_frame_equal(df, expected)
+
+    def test_construction_from_set(self):
+        # https://github.com/pandas-dev/pandas/issues/32582
+        result = pd.DataFrame({"a": {1, 2, 3}})
+        expected = pd.DataFrame({"a": [1, 2, 3]})
+
+        tm.assert_frame_equal(result, expected)