Fix DataFrame constructor to broadcast scalar inputs properly (#12997)

Fixes: #12646

This PR fixes an issue with `DataFrame` where broadcasting scalar inputs was order dependent.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Lawrence Mitchell (https://github.com/wence-)

URL: #12997

python/cudf/cudf/core/dataframe.py

@@ -907,14 +907,24 @@ def _init_from_dict_like(
         if index is None:
             num_rows = 0
             if data:
-                col_name = next(iter(data))
-                if is_scalar(data[col_name]):
-                    num_rows = num_rows or 1
-                else:
-                    data[col_name] = column.as_column(
-                        data[col_name], nan_as_null=nan_as_null
+                keys, values, lengths = zip(
+                    *(
+                        (k, v, 1)
+                        if is_scalar(v)
+                        else (
+                            k,
+                            vc := as_column(v, nan_as_null=nan_as_null),
+                            len(vc),
+                        )
+                        for k, v in data.items()
                     )
-                    num_rows = len(data[col_name])
+                )
+                data = dict(zip(keys, values))
+                try:
+                    (num_rows,) = (set(lengths) - {1}) or {1}
+                except ValueError:
+                    raise ValueError("All arrays must be the same length")
+
             self._index = RangeIndex(0, num_rows)
         else:
             self._index = as_index(index)

python/cudf/cudf/tests/test_dataframe.py

@@ -10057,3 +10057,33 @@ def test_dataframe_from_arrow_slice():
     actual = cudf.DataFrame.from_arrow(table_slice)
 
     assert_eq(expected, actual)
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        {"a": [1, 2, 3], "b": ["x", "y", "z"], "c": 4},
+        {"c": 4, "a": [1, 2, 3], "b": ["x", "y", "z"]},
+        {"a": [1, 2, 3], "c": 4},
+    ],
+)
+def test_dataframe_init_from_scalar_and_lists(data):
+    actual = cudf.DataFrame(data)
+    expected = pd.DataFrame(data)
+
+    assert_eq(expected, actual)
+
+
+def test_dataframe_init_length_error():
+    assert_exceptions_equal(
+        lfunc=pd.DataFrame,
+        rfunc=cudf.DataFrame,
+        lfunc_args_and_kwargs=(
+            [],
+            {"data": {"a": [1, 2, 3], "b": ["x", "y", "z", "z"], "c": 4}},
+        ),
+        rfunc_args_and_kwargs=(
+            [],
+            {"data": {"a": [1, 2, 3], "b": ["x", "y", "z", "z"], "c": 4}},
+        ),
+    )