From a641cce180342b8ca4d0db7b7683dc9439b645bb Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Fri, 14 Jan 2022 19:10:41 -0500
Subject: [PATCH 1/6] ENH: Allow safe access to `.book` in ExcelWriter

---
 pandas/io/excel/_base.py                |  1 -
 pandas/io/excel/_odswriter.py           | 12 +++++++++++-
 pandas/io/excel/_openpyxl.py            |  8 ++++----
 pandas/io/excel/_xlsxwriter.py          |  6 ++----
 pandas/io/excel/_xlwt.py                |  5 +++++
 pandas/tests/io/excel/test_odswriter.py | 10 ++++++++++
 pandas/tests/io/excel/test_openpyxl.py  |  9 +++++++++
 pandas/tests/io/excel/test_xlwt.py      |  9 +++++++++
 8 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/pandas/io/excel/_base.py b/pandas/io/excel/_base.py
index 3e1df9325713b..f22ff4b55eadb 100644
--- a/pandas/io/excel/_base.py
+++ b/pandas/io/excel/_base.py
@@ -1112,7 +1112,6 @@ def __init__(
             self.handles = get_handle(
                 path, mode, storage_options=storage_options, is_text=False
             )
-        self.sheets: dict[str, Any] = {}
         self.cur_sheet = None
 
         if date_format is None:
diff --git a/pandas/io/excel/_odswriter.py b/pandas/io/excel/_odswriter.py
index 0f31991ee29e9..e30548f220bbc 100644
--- a/pandas/io/excel/_odswriter.py
+++ b/pandas/io/excel/_odswriter.py
@@ -58,6 +58,16 @@ def __init__(
         self.book = OpenDocumentSpreadsheet(**engine_kwargs)
         self._style_dict: dict[str, str] = {}
 
+    @property
+    def sheets(self) -> dict[str, Any]:
+        from odf.table import Table
+
+        result = {
+            sheet.getAttribute("name"): sheet
+            for sheet in self.book.getElementsByType(Table)
+        }
+        return result
+
     def save(self) -> None:
         """
         Save workbook to disk.
@@ -91,7 +101,7 @@ def write_cells(
             wks = self.sheets[sheet_name]
         else:
             wks = Table(name=sheet_name)
-            self.sheets[sheet_name] = wks
+            self.book.spreadsheet.addElement(wks)
 
         if validate_freeze_panes(freeze_panes):
             freeze_panes = cast(Tuple[int, int], freeze_panes)
diff --git a/pandas/io/excel/_openpyxl.py b/pandas/io/excel/_openpyxl.py
index 88a25d1c1e6ef..c91ee6398c57d 100644
--- a/pandas/io/excel/_openpyxl.py
+++ b/pandas/io/excel/_openpyxl.py
@@ -68,8 +68,6 @@ def __init__(
 
             self.book = load_workbook(self.handles.handle, **engine_kwargs)
             self.handles.handle.seek(0)
-            self.sheets = {name: self.book[name] for name in self.book.sheetnames}
-
         else:
             # Create workbook object with default optimized_write=True.
             self.book = Workbook(**engine_kwargs)
@@ -77,6 +75,10 @@ def __init__(
             if self.book.worksheets:
                 self.book.remove(self.book.worksheets[0])
 
+    @property
+    def sheets(self) -> dict[str, Any]:
+        return {name: self.book[name] for name in self.book.sheetnames}
+
     def save(self) -> None:
         """
         Save workbook to disk.
@@ -440,7 +442,6 @@ def write_cells(
                     target_index = self.book.index(old_wks)
                     del self.book[sheet_name]
                     wks = self.book.create_sheet(sheet_name, target_index)
-                    self.sheets[sheet_name] = wks
                 elif self.if_sheet_exists == "error":
                     raise ValueError(
                         f"Sheet '{sheet_name}' already exists and "
@@ -458,7 +459,6 @@ def write_cells(
         else:
             wks = self.book.create_sheet()
             wks.title = sheet_name
-            self.sheets[sheet_name] = wks
 
         if validate_freeze_panes(freeze_panes):
             freeze_panes = cast(Tuple[int, int], freeze_panes)
diff --git a/pandas/io/excel/_xlsxwriter.py b/pandas/io/excel/_xlsxwriter.py
index 49c87732f1429..bbdf11e345989 100644
--- a/pandas/io/excel/_xlsxwriter.py
+++ b/pandas/io/excel/_xlsxwriter.py
@@ -222,11 +222,9 @@ def write_cells(
         # Write the frame cells using xlsxwriter.
         sheet_name = self._get_sheet_name(sheet_name)
 
-        if sheet_name in self.sheets:
-            wks = self.sheets[sheet_name]
-        else:
+        wks = self.book.get_worksheet_by_name(sheet_name)
+        if wks is None:
             wks = self.book.add_worksheet(sheet_name)
-            self.sheets[sheet_name] = wks
 
         style_dict = {"null": None}
 
diff --git a/pandas/io/excel/_xlwt.py b/pandas/io/excel/_xlwt.py
index 1ada0eb25f81c..239eff10d81a9 100644
--- a/pandas/io/excel/_xlwt.py
+++ b/pandas/io/excel/_xlwt.py
@@ -63,6 +63,11 @@ def __init__(
         self.fm_datetime = xlwt.easyxf(num_format_str=self.datetime_format)
         self.fm_date = xlwt.easyxf(num_format_str=self.date_format)
 
+    @property
+    def sheets(self) -> dict[str, Any]:
+        result = {sheet.name: sheet for sheet in self.book._Workbook__worksheets}
+        return result
+
     def save(self) -> None:
         """
         Save workbook to disk.
diff --git a/pandas/tests/io/excel/test_odswriter.py b/pandas/tests/io/excel/test_odswriter.py
index 0e6d1dac55506..d7348d8677a79 100644
--- a/pandas/tests/io/excel/test_odswriter.py
+++ b/pandas/tests/io/excel/test_odswriter.py
@@ -56,3 +56,13 @@ def test_engine_kwargs(ext, engine_kwargs):
         else:
             with ExcelWriter(f, engine="odf", engine_kwargs=engine_kwargs) as _:
                 pass
+
+
+def test_book_and_sheets_consistent(ext):
+    # GH#??? - Ensure sheets is updated if user modifies book
+    with tm.ensure_clean(ext) as f:
+        writer = ExcelWriter(f)
+        assert writer.sheets == {}
+        table = odf.table.Table(name="test_name")
+        writer.book.spreadsheet.addElement(table)
+        assert writer.sheets == {"test_name": table}
diff --git a/pandas/tests/io/excel/test_openpyxl.py b/pandas/tests/io/excel/test_openpyxl.py
index 9f6e1ed9c08d9..0689bc5fe90be 100644
--- a/pandas/tests/io/excel/test_openpyxl.py
+++ b/pandas/tests/io/excel/test_openpyxl.py
@@ -379,3 +379,12 @@ def test_read_empty_with_blank_row(datapath, ext, read_only):
             result = pd.read_excel(wb, engine="openpyxl")
     expected = DataFrame()
     tm.assert_frame_equal(result, expected)
+
+
+def test_book_and_sheets_consistent(ext):
+    # GH#??? - Ensure sheets is updated if user modifies book
+    with tm.ensure_clean(ext) as f:
+        writer = ExcelWriter(f, engine="openpyxl")
+        assert writer.sheets == {}
+        sheet = writer.book.create_sheet("test_name", 0)
+        assert writer.sheets == {"test_name": sheet}
diff --git a/pandas/tests/io/excel/test_xlwt.py b/pandas/tests/io/excel/test_xlwt.py
index ec333defd85ac..e22616952d69d 100644
--- a/pandas/tests/io/excel/test_xlwt.py
+++ b/pandas/tests/io/excel/test_xlwt.py
@@ -125,3 +125,12 @@ def test_engine_kwargs(ext, style_compression):
             assert writer.book._Workbook__styles.style_compression == style_compression
             # xlwt won't allow us to close without writing something
             DataFrame().to_excel(writer)
+
+
+def test_book_and_sheets_consistent(ext):
+    # GH#??? - Ensure sheets is updated if user modifies book
+    with tm.ensure_clean(ext) as f:
+        writer = ExcelWriter(f)
+        assert writer.sheets == {}
+        sheet = writer.book.add_sheet("test_name")
+        assert writer.sheets == {"test_name": sheet}

From ba7ff3567d6ff5abb5add27c1e9f8946770631d8 Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Fri, 28 Jan 2022 17:28:17 -0500
Subject: [PATCH 2/6] Add GH # in tests

---
 pandas/tests/io/excel/test_odswriter.py | 2 +-
 pandas/tests/io/excel/test_openpyxl.py  | 2 +-
 pandas/tests/io/excel/test_xlwt.py      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/tests/io/excel/test_odswriter.py b/pandas/tests/io/excel/test_odswriter.py
index d7348d8677a79..c52a7c9e9caca 100644
--- a/pandas/tests/io/excel/test_odswriter.py
+++ b/pandas/tests/io/excel/test_odswriter.py
@@ -59,7 +59,7 @@ def test_engine_kwargs(ext, engine_kwargs):
 
 
 def test_book_and_sheets_consistent(ext):
-    # GH#??? - Ensure sheets is updated if user modifies book
+    # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
         writer = ExcelWriter(f)
         assert writer.sheets == {}
diff --git a/pandas/tests/io/excel/test_openpyxl.py b/pandas/tests/io/excel/test_openpyxl.py
index 0689bc5fe90be..a5bacaa593ad7 100644
--- a/pandas/tests/io/excel/test_openpyxl.py
+++ b/pandas/tests/io/excel/test_openpyxl.py
@@ -382,7 +382,7 @@ def test_read_empty_with_blank_row(datapath, ext, read_only):
 
 
 def test_book_and_sheets_consistent(ext):
-    # GH#??? - Ensure sheets is updated if user modifies book
+    # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
         writer = ExcelWriter(f, engine="openpyxl")
         assert writer.sheets == {}
diff --git a/pandas/tests/io/excel/test_xlwt.py b/pandas/tests/io/excel/test_xlwt.py
index e22616952d69d..3827367348e41 100644
--- a/pandas/tests/io/excel/test_xlwt.py
+++ b/pandas/tests/io/excel/test_xlwt.py
@@ -128,7 +128,7 @@ def test_engine_kwargs(ext, style_compression):
 
 
 def test_book_and_sheets_consistent(ext):
-    # GH#??? - Ensure sheets is updated if user modifies book
+    # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
         writer = ExcelWriter(f)
         assert writer.sheets == {}

From 8f433f02eb1f05294d89459e6cf91144bca70d16 Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Sat, 29 Jan 2022 07:20:37 -0500
Subject: [PATCH 3/6] Use context manager in tests

---
 pandas/tests/io/excel/test_odswriter.py | 10 +++++-----
 pandas/tests/io/excel/test_openpyxl.py  |  8 ++++----
 pandas/tests/io/excel/test_xlwt.py      |  8 ++++----
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/pandas/tests/io/excel/test_odswriter.py b/pandas/tests/io/excel/test_odswriter.py
index c52a7c9e9caca..e9dad0c7fedc9 100644
--- a/pandas/tests/io/excel/test_odswriter.py
+++ b/pandas/tests/io/excel/test_odswriter.py
@@ -61,8 +61,8 @@ def test_engine_kwargs(ext, engine_kwargs):
 def test_book_and_sheets_consistent(ext):
     # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
-        writer = ExcelWriter(f)
-        assert writer.sheets == {}
-        table = odf.table.Table(name="test_name")
-        writer.book.spreadsheet.addElement(table)
-        assert writer.sheets == {"test_name": table}
+        with ExcelWriter(f) as writer:
+            assert writer.sheets == {}
+            table = odf.table.Table(name="test_name")
+            writer.book.spreadsheet.addElement(table)
+            assert writer.sheets == {"test_name": table}
diff --git a/pandas/tests/io/excel/test_openpyxl.py b/pandas/tests/io/excel/test_openpyxl.py
index a5bacaa593ad7..e1c68eeaee356 100644
--- a/pandas/tests/io/excel/test_openpyxl.py
+++ b/pandas/tests/io/excel/test_openpyxl.py
@@ -384,7 +384,7 @@ def test_read_empty_with_blank_row(datapath, ext, read_only):
 def test_book_and_sheets_consistent(ext):
     # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
-        writer = ExcelWriter(f, engine="openpyxl")
-        assert writer.sheets == {}
-        sheet = writer.book.create_sheet("test_name", 0)
-        assert writer.sheets == {"test_name": sheet}
+        with ExcelWriter(f, engine="openpyxl") as writer:
+            assert writer.sheets == {}
+            sheet = writer.book.create_sheet("test_name", 0)
+            assert writer.sheets == {"test_name": sheet}
diff --git a/pandas/tests/io/excel/test_xlwt.py b/pandas/tests/io/excel/test_xlwt.py
index 3827367348e41..2d5386d6c616d 100644
--- a/pandas/tests/io/excel/test_xlwt.py
+++ b/pandas/tests/io/excel/test_xlwt.py
@@ -130,7 +130,7 @@ def test_engine_kwargs(ext, style_compression):
 def test_book_and_sheets_consistent(ext):
     # GH#45687 - Ensure sheets is updated if user modifies book
     with tm.ensure_clean(ext) as f:
-        writer = ExcelWriter(f)
-        assert writer.sheets == {}
-        sheet = writer.book.add_sheet("test_name")
-        assert writer.sheets == {"test_name": sheet}
+        with ExcelWriter(f) as writer:
+            assert writer.sheets == {}
+            sheet = writer.book.add_sheet("test_name")
+            assert writer.sheets == {"test_name": sheet}

From 7ede1a85528dec4e22acd1490a224875b61a70b6 Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Sun, 30 Jan 2022 11:41:45 -0500
Subject: [PATCH 4/6] Add back xlsxwriter sheets, add tests

---
 pandas/io/excel/_openpyxl.py             | 3 ++-
 pandas/io/excel/_xlsxwriter.py           | 5 +++++
 pandas/tests/io/excel/test_xlsxwriter.py | 9 +++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/pandas/io/excel/_openpyxl.py b/pandas/io/excel/_openpyxl.py
index c91ee6398c57d..475f78b012373 100644
--- a/pandas/io/excel/_openpyxl.py
+++ b/pandas/io/excel/_openpyxl.py
@@ -77,7 +77,8 @@ def __init__(
 
     @property
     def sheets(self) -> dict[str, Any]:
-        return {name: self.book[name] for name in self.book.sheetnames}
+        result = {name: self.book[name] for name in self.book.sheetnames}
+        return result
 
     def save(self) -> None:
         """
diff --git a/pandas/io/excel/_xlsxwriter.py b/pandas/io/excel/_xlsxwriter.py
index bbdf11e345989..dbd6264827591 100644
--- a/pandas/io/excel/_xlsxwriter.py
+++ b/pandas/io/excel/_xlsxwriter.py
@@ -205,6 +205,11 @@ def __init__(
 
         self.book = Workbook(self.handles.handle, **engine_kwargs)
 
+    @property
+    def sheets(self) -> dict[str, Any]:
+        result = self.book.sheetnames
+        return result
+
     def save(self) -> None:
         """
         Save workbook to disk.
diff --git a/pandas/tests/io/excel/test_xlsxwriter.py b/pandas/tests/io/excel/test_xlsxwriter.py
index b5c1b47775089..82d47a13aefbc 100644
--- a/pandas/tests/io/excel/test_xlsxwriter.py
+++ b/pandas/tests/io/excel/test_xlsxwriter.py
@@ -83,3 +83,12 @@ def test_engine_kwargs(ext, nan_inf_to_errors):
     with tm.ensure_clean(ext) as f:
         with ExcelWriter(f, engine="xlsxwriter", engine_kwargs=engine_kwargs) as writer:
             assert writer.book.nan_inf_to_errors == nan_inf_to_errors
+
+
+def test_book_and_sheets_consistent(ext):
+    # GH#45687 - Ensure sheets is updated if user modifies book
+    with tm.ensure_clean(ext) as f:
+        with ExcelWriter(f, engine="xlsxwriter") as writer:
+            assert writer.sheets == {}
+            sheet = writer.book.add_worksheet("test_name")
+            assert writer.sheets == {"test_name": sheet}

From 61c92c2fe78ad627008e76927a5eca65b801f68b Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Sun, 30 Jan 2022 11:53:59 -0500
Subject: [PATCH 5/6] Add sheets as an abstract property

---
 pandas/io/excel/_base.py              | 6 ++++++
 pandas/tests/io/excel/test_writers.py | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/pandas/io/excel/_base.py b/pandas/io/excel/_base.py
index f22ff4b55eadb..ea459f13dfdc0 100644
--- a/pandas/io/excel/_base.py
+++ b/pandas/io/excel/_base.py
@@ -1048,6 +1048,12 @@ def engine(self) -> str:
         """Name of engine."""
         pass
 
+    @property
+    @abc.abstractmethod
+    def sheets(self) -> dict[str, Any]:
+        """Mapping of sheet name to sheet object."""
+        pass
+
     @abc.abstractmethod
     def write_cells(
         self,
diff --git a/pandas/tests/io/excel/test_writers.py b/pandas/tests/io/excel/test_writers.py
index 6f06ef9c09e52..7a95dcb4e3a72 100644
--- a/pandas/tests/io/excel/test_writers.py
+++ b/pandas/tests/io/excel/test_writers.py
@@ -1271,10 +1271,12 @@ def test_register_writer(self):
         # some awkward mocking to test out dispatch and such actually works
         called_save = []
         called_write_cells = []
+        called_sheets = []
 
         class DummyClass(ExcelWriter):
             called_save = False
             called_write_cells = False
+            called_sheets = False
             supported_extensions = ["xlsx", "xls"]
             engine = "dummy"
 
@@ -1284,12 +1286,18 @@ def save(self):
             def write_cells(self, *args, **kwargs):
                 called_write_cells.append(True)
 
+            @property
+            def sheets(self):
+                called_sheets.append(True)
+
         def check_called(func):
             func()
             assert len(called_save) >= 1
             assert len(called_write_cells) >= 1
+            assert len(called_sheets) == 0
             del called_save[:]
             del called_write_cells[:]
+            del called_sheets[:]
 
         with option_context("io.excel.xlsx.writer", "dummy"):
             path = "something.xlsx"

From d8415bfa4f32d570590a8595cbad8df98dde2f24 Mon Sep 17 00:00:00 2001
From: Richard Shadrach <rhshadrach@gmail.com>
Date: Mon, 31 Jan 2022 16:03:00 -0500
Subject: [PATCH 6/6] docstrings

---
 pandas/io/excel/_base.py      | 2 +-
 pandas/io/excel/_odswriter.py | 1 +
 pandas/io/excel/_openpyxl.py  | 1 +
 pandas/io/excel/_xlwt.py      | 1 +
 4 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/pandas/io/excel/_base.py b/pandas/io/excel/_base.py
index ea459f13dfdc0..b33955737a111 100644
--- a/pandas/io/excel/_base.py
+++ b/pandas/io/excel/_base.py
@@ -1051,7 +1051,7 @@ def engine(self) -> str:
     @property
     @abc.abstractmethod
     def sheets(self) -> dict[str, Any]:
-        """Mapping of sheet name to sheet object."""
+        """Mapping of sheet names to sheet objects."""
         pass
 
     @abc.abstractmethod
diff --git a/pandas/io/excel/_odswriter.py b/pandas/io/excel/_odswriter.py
index e30548f220bbc..9069a37ccb5af 100644
--- a/pandas/io/excel/_odswriter.py
+++ b/pandas/io/excel/_odswriter.py
@@ -60,6 +60,7 @@ def __init__(
 
     @property
     def sheets(self) -> dict[str, Any]:
+        """Mapping of sheet names to sheet objects."""
         from odf.table import Table
 
         result = {
diff --git a/pandas/io/excel/_openpyxl.py b/pandas/io/excel/_openpyxl.py
index 475f78b012373..4b03c2536b31b 100644
--- a/pandas/io/excel/_openpyxl.py
+++ b/pandas/io/excel/_openpyxl.py
@@ -77,6 +77,7 @@ def __init__(
 
     @property
     def sheets(self) -> dict[str, Any]:
+        """Mapping of sheet names to sheet objects."""
         result = {name: self.book[name] for name in self.book.sheetnames}
         return result
 
diff --git a/pandas/io/excel/_xlwt.py b/pandas/io/excel/_xlwt.py
index 239eff10d81a9..fe2addc890c22 100644
--- a/pandas/io/excel/_xlwt.py
+++ b/pandas/io/excel/_xlwt.py
@@ -65,6 +65,7 @@ def __init__(
 
     @property
     def sheets(self) -> dict[str, Any]:
+        """Mapping of sheet names to sheet objects."""
         result = {sheet.name: sheet for sheet in self.book._Workbook__worksheets}
         return result