DEPR: Change read_excel sheetname to sheet_name (#16442)

* GH10559: Minor improvement: Change to_excel sheet name

modify io/excel.py and relevant docs (io.rst) to use sheet_name for read_excel
but allow sheetname to still be used for backwards compatibility.  add test_excel
to verify that sheet_name and sheetname args produce the same result.

* GH10559: Minor improvement: Change to_excel sheet name

added @deprecate_kwarg to read_excel as arg changes from sheetname to sheet_name.
moved test comments into function, add assert_produces_warning.

* GH10559: Minor improvement: Change to_excel sheet name

remove manual arg change, use @deprecate_kwarg to read_excel
as arg changes from sheetname to sheet_name.

* GH10559: Minor improvement: Change to_excel sheet name

shorten lines under 79 char.

* GH10559: Minor improvement: Change to_excel sheet name

update whats new 0.21.0 Deprecations section noting sheetname deprecated
in favor of sheet_name.
add sheetname deprecation in read_excel() docstring.

doc/source/io.rst

@@ -2561,12 +2561,12 @@ Reading Excel Files
 '''''''''''''''''''
 
 In the most basic use-case, ``read_excel`` takes a path to an Excel
-file, and the ``sheetname`` indicating which sheet to parse.
+file, and the ``sheet_name`` indicating which sheet to parse.
 
 .. code-block:: python
 
    # Returns a DataFrame
-   read_excel('path_to_file.xls', sheetname='Sheet1')
+   read_excel('path_to_file.xls', sheet_name='Sheet1')
 
 
 .. _io.excel.excelfile_class:
@@ -2634,12 +2634,12 @@ of sheet names can simply be passed to ``read_excel`` with no loss in performanc
 Specifying Sheets
 +++++++++++++++++
 
-.. note :: The second argument is ``sheetname``, not to be confused with ``ExcelFile.sheet_names``
+.. note :: The second argument is ``sheet_name``, not to be confused with ``ExcelFile.sheet_names``
 
 .. note :: An ExcelFile's attribute ``sheet_names`` provides access to a list of sheets.
 
-- The arguments ``sheetname`` allows specifying the sheet or sheets to read.
-- The default value for ``sheetname`` is 0, indicating to read the first sheet
+- The arguments ``sheet_name`` allows specifying the sheet or sheets to read.
+- The default value for ``sheet_name`` is 0, indicating to read the first sheet
 - Pass a string to refer to the name of a particular sheet in the workbook.
 - Pass an integer to refer to the index of a sheet. Indices follow Python
   convention, beginning at 0.
@@ -2670,18 +2670,18 @@ Using None to get all sheets:
 .. code-block:: python
 
    # Returns a dictionary of DataFrames
-   read_excel('path_to_file.xls',sheetname=None)
+   read_excel('path_to_file.xls',sheet_name=None)
 
 Using a list to get multiple sheets:
 
 .. code-block:: python
 
    # Returns the 1st and 4th sheet, as a dictionary of DataFrames.
-   read_excel('path_to_file.xls',sheetname=['Sheet1',3])
+   read_excel('path_to_file.xls',sheet_name=['Sheet1',3])
 
 .. versionadded:: 0.16
 
-``read_excel`` can read more than one sheet, by setting ``sheetname`` to either
+``read_excel`` can read more than one sheet, by setting ``sheet_name`` to either
 a list of sheet names, a list of sheet positions, or ``None`` to read all sheets.
 
 .. versionadded:: 0.13

doc/source/whatsnew/v0.21.0.txt

@@ -59,7 +59,7 @@ Other API Changes
 
 Deprecations
 ~~~~~~~~~~~~
-
+- :func:`read_excel()` has deprecated ``sheetname`` in favor of ``sheet_name`` for consistency with to_excel() (:issue:`10559`).
 
 
 .. _whatsnew_0210.prior_deprecations:

pandas/io/excel.py

@@ -30,7 +30,7 @@
 import pandas.compat.openpyxl_compat as openpyxl_compat
 from warnings import warn
 from distutils.version import LooseVersion
-from pandas.util._decorators import Appender
+from pandas.util._decorators import Appender, deprecate_kwarg
 from textwrap import fill
 
 __all__ = ["read_excel", "ExcelWriter", "ExcelFile"]
@@ -48,7 +48,7 @@
     The string could be a URL. Valid URL schemes include http, ftp, s3,
     and file. For file URLs, a host is expected. For instance, a local
     file could be file://localhost/path/to/workbook.xlsx
-sheetname : string, int, mixed list of strings/ints, or None, default 0
+sheet_name : string, int, mixed list of strings/ints, or None, default 0
 
     Strings are used for sheet names, Integers are used in zero-indexed
     sheet positions.
@@ -69,6 +69,10 @@
     * [0,1,"Sheet5"] -> 1st, 2nd & 5th sheet as a dictionary of DataFrames
     * None -> All sheets as a dictionary of DataFrames
 
+sheetname : string, int, mixed list of strings/ints, or None, default 0
+    .. deprecated:: 0.21.0
+       Use `sheet_name` instead
+
 header : int, list of ints, default 0
     Row (0-indexed) to use for the column labels of the parsed
     DataFrame. If a list of integers is passed those row positions will
@@ -144,7 +148,7 @@
 Returns
 -------
 parsed : DataFrame or Dict of DataFrames
-    DataFrame from the passed in Excel file.  See notes in sheetname
+    DataFrame from the passed in Excel file.  See notes in sheet_name
     argument for more information on when a Dict of Dataframes is returned.
 """
 
@@ -189,8 +193,9 @@ def get_writer(engine_name):
         raise ValueError("No Excel writer '%s'" % engine_name)
 
 
+@deprecate_kwarg('sheetname', 'sheet_name')
 @Appender(_read_excel_doc)
-def read_excel(io, sheetname=0, header=0, skiprows=None, skip_footer=0,
+def read_excel(io, sheet_name=0, header=0, skiprows=None, skip_footer=0,
                index_col=None, names=None, parse_cols=None, parse_dates=False,
                date_parser=None, na_values=None, thousands=None,
                convert_float=True, has_index_names=None, converters=None,
@@ -201,7 +206,7 @@ def read_excel(io, sheetname=0, header=0, skiprows=None, skip_footer=0,
         io = ExcelFile(io, engine=engine)
 
     return io._parse_excel(
-        sheetname=sheetname, header=header, skiprows=skiprows, names=names,
+        sheetname=sheet_name, header=header, skiprows=skiprows, names=names,
         index_col=index_col, parse_cols=parse_cols, parse_dates=parse_dates,
         date_parser=date_parser, na_values=na_values, thousands=thousands,
         convert_float=convert_float, has_index_names=has_index_names,
@@ -266,7 +271,7 @@ def __init__(self, io, **kwds):
     def __fspath__(self):
         return self._io
 
-    def parse(self, sheetname=0, header=0, skiprows=None, skip_footer=0,
+    def parse(self, sheet_name=0, header=0, skiprows=None, skip_footer=0,
               names=None, index_col=None, parse_cols=None, parse_dates=False,
               date_parser=None, na_values=None, thousands=None,
               convert_float=True, has_index_names=None,
@@ -279,7 +284,7 @@ def parse(self, sheetname=0, header=0, skiprows=None, skip_footer=0,
         docstring for more info on accepted parameters
         """
 
-        return self._parse_excel(sheetname=sheetname, header=header,
+        return self._parse_excel(sheetname=sheet_name, header=header,
                                  skiprows=skiprows, names=names,
                                  index_col=index_col,
                                  has_index_names=has_index_names,

pandas/tests/io/test_excel.py

@@ -544,6 +544,18 @@ def test_date_conversion_overflow(self):
         result = self.get_exceldf('testdateoverflow')
         tm.assert_frame_equal(result, expected)
 
+    def test_sheet_name_and_sheetname(self):
+        # GH10559: Minor improvement: Change "sheet_name" to "sheetname"
+        # GH10969: DOC: Consistent var names (sheetname vs sheet_name)
+        # GH12604: CLN GH10559 Rename sheetname variable to sheet_name
+        dfref = self.get_csv_refdf('test1')
+        df1 = self.get_exceldf('test1', sheet_name='Sheet1')    # doc
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            df2 = self.get_exceldf('test1', sheetname='Sheet2')  # bkwrd compat
+
+        tm.assert_frame_equal(df1, dfref, check_names=False)
+        tm.assert_frame_equal(df2, dfref, check_names=False)
+
 
 class XlrdTests(ReadingTestsBase):
     """