deprecate positional args in read_csv (#41657)

Co-authored-by: Marco Gorelli <[email protected]>
Co-authored-by: Simon Hawkins <[email protected]>

Author: 3 people

doc/source/whatsnew/v1.3.0.rst

@@ -697,6 +697,7 @@ Deprecations
 - Deprecated construction of :class:`Series` or :class:`DataFrame` with ``DatetimeTZDtype`` data and ``datetime64[ns]`` dtype.  Use ``Series(data).dt.tz_localize(None)`` instead (:issue:`41555`,:issue:`33401`)
 - Deprecated passing arguments as positional in :meth:`DataFrame.set_axis` and :meth:`Series.set_axis` (other than ``"labels"``) (:issue:`41485`)
 - Deprecated passing arguments as positional in :meth:`DataFrame.where` and :meth:`Series.where` (other than ``"cond"`` and ``"other"``) (:issue:`41485`)
+- Deprecated passing arguments as positional (other than ``filepath_or_buffer``) in :func:`read_csv` (:issue:`41485`)
 - Deprecated passing arguments as positional in :meth:`DataFrame.drop` (other than ``"labels"``) and :meth:`Series.drop` (:issue:`41485`)
 -
 

pandas/io/parsers/readers.py

@@ -30,7 +30,10 @@
     AbstractMethodError,
     ParserWarning,
 )
-from pandas.util._decorators import Appender
+from pandas.util._decorators import (
+    Appender,
+    deprecate_nonkeyword_arguments,
+)
 
 from pandas.core.dtypes.common import (
     is_file_like,
@@ -472,6 +475,9 @@ def _read(filepath_or_buffer: FilePathOrBuffer, kwds):
         return parser.read(nrows)
 
 
+@deprecate_nonkeyword_arguments(
+    version=None, allowed_args=["filepath_or_buffer"], stacklevel=3
+)
 @Appender(
     _doc_read_csv_and_table.format(
         func_name="read_csv",

pandas/tests/io/parser/common/test_common_basic.py

@@ -733,6 +733,18 @@ def test_read_csv_delimiter_and_sep_no_default(all_parsers):
         parser.read_csv(f, sep=" ", delimiter=".")
 
 
+def test_read_csv_posargs_deprecation(all_parsers):
+    # GH 41485
+    f = StringIO("a,b\n1,2")
+    parser = all_parsers
+    msg = (
+        "In a future version of pandas all arguments of read_csv "
+        "except for the argument 'filepath_or_buffer' will be keyword-only"
+    )
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        parser.read_csv(f, " ")
+
+
 @pytest.mark.parametrize("delimiter", [",", "\t"])
 def test_read_table_delim_whitespace_non_default_sep(all_parsers, delimiter):
     # GH: 35958