EHN: handle frozenset in pprint (#60828)

* Add test

* handle frozenset

* add whatsnew

* Update doc/source/whatsnew/v3.0.0.rst

Co-authored-by: Matthew Roeschke <[email protected]>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Matthew Roeschke <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

doc/source/whatsnew/v3.0.0.rst

@@ -68,6 +68,7 @@ Other enhancements
 - :meth:`Series.map` can now accept kwargs to pass on to func (:issue:`59814`)
 - :meth:`Series.str.get_dummies` now accepts a  ``dtype`` parameter to specify the dtype of the resulting DataFrame (:issue:`47872`)
 - :meth:`pandas.concat` will raise a ``ValueError`` when ``ignore_index=True`` and ``keys`` is not ``None`` (:issue:`59274`)
+- :py:class:`frozenset` elements in pandas objects are now natively printed (:issue:`60690`)
 - Implemented :meth:`Series.str.isascii` and :meth:`Series.str.isascii` (:issue:`59091`)
 - Multiplying two :class:`DateOffset` objects will now raise a ``TypeError`` instead of a ``RecursionError`` (:issue:`59442`)
 - Restore support for reading Stata 104-format and enable reading 103-format dta files (:issue:`58554`)

pandas/io/formats/printing.py

@@ -111,6 +111,8 @@ def _pprint_seq(
     """
     if isinstance(seq, set):
         fmt = "{{{body}}}"
+    elif isinstance(seq, frozenset):
+        fmt = "frozenset({body})"
     else:
         fmt = "[{body}]" if hasattr(seq, "__setitem__") else "({body})"
 

pandas/tests/io/formats/test_printing.py

@@ -82,6 +82,9 @@ def test_repr_dict(self):
     def test_repr_mapping(self):
         assert printing.pprint_thing(MyMapping()) == "{'a': 4, 'b': 4}"
 
+    def test_repr_frozenset(self):
+        assert printing.pprint_thing(frozenset([1, 2])) == "frozenset(1, 2)"
+
 
 class TestFormatBase:
     def test_adjoin(self):