Merge branch 'master' of https://github.com/pandas-dev/pandas into op…

…enpyxl_workbook � Conflicts: � doc/source/whatsnew/v1.2.2.rst � pandas/tests/io/excel/test_openpyxl.py
pandas-dev · jreback · Feb 7, 2021 · Feb 3, 2021 · Feb 3, 2021 · Feb 3, 2021
commit 1f16602000f5cce3cbcb87bfd2f000b65d036288
diff --git a/doc/source/whatsnew/v1.2.2.rst b/doc/source/whatsnew/v1.2.2.rst
@@ -21,7 +21,9 @@ Fixed regressions
 - Fixed regression in :meth:`~DataFrame.to_pickle` failing to create bz2/xz compressed pickle files with ``protocol=5`` (:issue:`39002`)
 - Fixed regression in :func:`pandas.testing.assert_series_equal` and :func:`pandas.testing.assert_frame_equal` always raising ``AssertionError`` when comparing extension dtypes (:issue:`39410`)
 - Fixed regression in :meth:`~DataFrame.to_csv` opening ``codecs.StreamWriter`` in binary mode instead of in text mode and ignoring user-provided ``mode`` (:issue:`39247`)
+- Fixed regression in :meth:`core.window.rolling.Rolling.count` where the ``min_periods`` argument would be set to ``0`` after the operation (:issue:`39554`)
 - Fixed regression in :func:`read_excel` that incorrectly raised when the argument ``io`` was a non-path and non-buffer and the ``engine`` argument was specified (:issue:`39528`)
+-
 
 .. ---------------------------------------------------------------------------
 

diff --git a/pandas/tests/io/excel/test_openpyxl.py b/pandas/tests/io/excel/test_openpyxl.py
@@ -122,6 +122,35 @@ def test_to_excel_with_openpyxl_engine(ext):
         styled.to_excel(filename, engine="openpyxl")
 
 
+@pytest.mark.parametrize(
+    "header, expected_data",
+    [
+        (
+            0,
+            {
+                "Title": [np.nan, "A", 1, 2, 3],
+                "Unnamed: 1": [np.nan, "B", 4, 5, 6],
+                "Unnamed: 2": [np.nan, "C", 7, 8, 9],
+            },
+        ),
+        (2, {"A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]}),
+    ],
+)
+@pytest.mark.parametrize(
+    "filename", ["dimension_missing", "dimension_small", "dimension_large"]
+)
+@pytest.mark.xfail(
+    LooseVersion(get_version(openpyxl)) < "3.0.0",
+    reason="openpyxl read-only sheet is incorrect when dimension data is wrong",
+)
+def test_read_with_bad_dimension(datapath, ext, header, expected_data, filename):
+    # GH 38956, 39001 - no/incorrect dimension information
+    path = datapath("io", "data", "excel", f"{filename}{ext}")
+    result = pd.read_excel(path, header=header)
+    expected = DataFrame(expected_data)
+    tm.assert_frame_equal(result, expected)
+
+
 def test_read_workbook(datapath, ext):
     # GH 39528
     filename = datapath("io", "data", "excel", "test1" + ext)