DEPR: deprecated nonkeyword arguments in to_csv (#54632)

deprecated nonkeyword arguments

doc/source/whatsnew/v2.2.0.rst

@@ -92,6 +92,7 @@ Other API changes
 
 Deprecations
 ~~~~~~~~~~~~
+- Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_csv` except ``path_or_buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_hdf` except ``path_or_buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_html` except ``buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_json` except ``path_or_buf``. (:issue:`54229`)

pandas/core/generic.py

@@ -3728,6 +3728,9 @@ def to_csv(
         ...
 
     @final
+    @deprecate_nonkeyword_arguments(
+        version="3.0", allowed_args=["self", "path_or_buf"], name="to_csv"
+    )
     @doc(
         storage_options=_shared_docs["storage_options"],
         compression_options=_shared_docs["compression_options"] % "path_or_buf",

pandas/tests/io/formats/test_to_csv.py

@@ -731,3 +731,15 @@ def test_to_csv_iterative_compression_buffer(compression):
             pd.read_csv(buffer, compression=compression, index_col=0), df
         )
         assert not buffer.closed
+
+
+def test_to_csv_pos_args_deprecation():
+    # GH-54229
+    df = DataFrame({"a": [1, 2, 3]})
+    msg = (
+        r"Starting with pandas version 3.0 all arguments of to_csv except for the "
+        r"argument 'path_or_buf' will be keyword-only."
+    )
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        buffer = io.BytesIO()
+        df.to_csv(buffer, ";")