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

…enpyxl_nans

� Conflicts:
�	pandas/tests/io/excel/test_openpyxl.py

pandas/tests/io/excel/test_openpyxl.py

@@ -172,6 +172,25 @@ def test_read_with_bad_dimension(
     tm.assert_frame_equal(result, expected)
 
 
+def test_append_mode_file(ext):
+    # GH 39576
+    df = DataFrame()
+
+    with tm.ensure_clean(ext) as f:
+        df.to_excel(f, engine="openpyxl")
+
+        with ExcelWriter(f, mode="a", engine="openpyxl") as writer:
+            df.to_excel(writer)
+
+        # make sure that zip files are not concatenated by making sure that
+        # "docProps/app.xml" only occurs twice in the file
+        data = Path(f).read_bytes()
+        first = data.find(b"docProps/app.xml")
+        second = data.find(b"docProps/app.xml", first + 1)
+        third = data.find(b"docProps/app.xml", second + 1)
+        assert second != -1 and third == -1
+
+
 def test_read_with_empty_trailing_rows(datapath, ext):
     # GH 39181
     path = datapath("io", "data", "excel", f"empty_trailing_rows{ext}")