BUG: Fix to_json when converting Period column

doc/source/whatsnew/v1.1.0.rst

@@ -529,6 +529,7 @@ I/O
 - Bug in :meth:`DataFrame.to_sql` where an ``AttributeError`` was raised when saving an out of bounds date (:issue:`26761`)
 - Bug in :meth:`read_excel` did not correctly handle multiple embedded spaces in OpenDocument text cells. (:issue:`32207`)
 - Bug in :meth:`read_json` was raising ``TypeError`` when reading a list of booleans into a Series. (:issue:`31464`)
+- Bug in :meth:`to_json` was raising ``AttributeError`` with column or Series of `PeriodDtype` (:issue:`31917`)
 
 Plotting
 ^^^^^^^^

pandas/conftest.py

@@ -473,6 +473,15 @@ def _create_series(index):
 }
 
 
+@pytest.fixture
+def period_series():
+    """Fixture for Series with Period-type index.
+    """
+    s = tm.makePeriodSeries()
+    s.name = 'ps'
+    return s
+
+
 @pytest.fixture
 def series_with_simple_index(indices):
     """

pandas/io/json/_table_schema.py

@@ -115,7 +115,7 @@ def convert_pandas_type_to_json_field(arr):
         field["constraints"] = {"enum": list(cats)}
         field["ordered"] = ordered
     elif is_period_dtype(arr):
-        field["freq"] = arr.freqstr
+        field["freq"] = arr.dtype.freq.freqstr
     elif is_datetime64tz_dtype(arr):
         if hasattr(arr, "dt"):
             field["tz"] = arr.dt.tz.zone

pandas/tests/io/json/test_pandas.py

@@ -650,6 +650,21 @@ def test_series_roundtrip_timeseries(self, orient, numpy, datetime_series):
 
         tm.assert_series_equal(result, expected)
 
+    def test_series_roundtrip_periodseries(self, orient, period_series):
+        # GH32665: Fix to_json when converting Period column/series
+        data = period_series.to_json(orient=orient)
+        result = pd.read_json(data, typ="series", orient=orient)
+
+        expected = period_series
+        if orient in ("values", "records"):
+            expected = expected.reset_index(drop=True)
+        if orient in ("index", "columns"):
+            result.index = result.index.to_period()
+        if orient != "split":
+            expected.name = None
+
+        tm.assert_series_equal(result, expected)
+
     @pytest.mark.parametrize("dtype", [np.float64, np.int])
     @pytest.mark.parametrize("numpy", [True, False])
     def test_series_roundtrip_numeric(self, orient, numpy, dtype):