add to_csv example, no method test, Optional types, tweaks; update wh…

…atsnew

doc/source/whatsnew/v0.25.0.rst

@@ -36,7 +36,7 @@ Other Enhancements
 - :class:`RangeIndex` has gained :attr:`~RangeIndex.start`, :attr:`~RangeIndex.stop`, and :attr:`~RangeIndex.step` attributes (:issue:`25710`)
 - :class:`datetime.timezone` objects are now supported as arguments to timezone methods and constructors (:issue:`25065`)
 - :meth:`DataFrame.query` and :meth:`DataFrame.eval` now supports quoting column names with backticks to refer to names with spaces (:issue:`6508`)
-- :meth:`NDFrame.to_csv` now supports dicts as ``compression`` argument with key ``'method'`` being the compression method and others as kwargs of ``ByteZipFile`` when the compression method is ``'zip'``. (:issue:`26023`)
+- :meth:`DataFrame.to_csv` and :meth:`Series.to_csv` now support dicts as ``compression`` argument with key ``'method'`` being the compression method and others as kwargs of ``ByteZipFile`` when the compression method is ``'zip'``. (:issue:`26023`)
 
 .. _whatsnew_0250.api_breaking:
 

pandas/core/generic.py

@@ -6,7 +6,7 @@
 import operator
 import pickle
 from textwrap import dedent
-from typing import Dict, FrozenSet, List, Set, Union
+from typing import Any, Dict, FrozenSet, List, Optional, Set, Union
 import warnings
 import weakref
 
@@ -2912,7 +2912,7 @@ def to_latex(self, buf=None, columns=None, col_space=None, header=True,
     def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
                columns=None, header=True, index=True, index_label=None,
                mode='w', encoding=None,
-               compression: Union[str, Dict, None] = 'infer',
+               compression: Optional[Union[str, Dict[str, Any]]] = 'infer',
                quoting=None, quotechar='"', line_terminator=None,
                chunksize=None, tupleize_cols=None, date_format=None,
                doublequote=True, escapechar=None, decimal='.'):
@@ -3028,6 +3028,10 @@ def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
         ...                    'weapon': ['sai', 'bo staff']})
         >>> df.to_csv(index=False)
         'name,mask,weapon\nRaphael,red,sai\nDonatello,purple,bo staff\n'
+        >>> compression_opts = dict(method='zip', archive_name='out.csv')
+        >>> df.to_csv('out.zip', index=False, compression=compression_opts)
+
+        # creates 'out.zip' containing 'out.csv'
         """
 
         df = self if isinstance(self, ABCDataFrame) else self.to_frame()

pandas/io/common.py

@@ -9,7 +9,7 @@
 import lzma
 import mmap
 import os
-from typing import Any, Dict, Tuple, Union
+from typing import Any, Dict, Optional, Tuple, Union
 from urllib.error import URLError  # noqa
 from urllib.parse import (  # noqa
     urlencode, urljoin, urlparse as parse_url, uses_netloc, uses_params,
@@ -233,7 +233,7 @@ def file_path_to_url(path):
 }
 
 
-def _get_compression_method(compression: Union[str, Dict, None]):
+def _get_compression_method(compression: Optional[Union[str, Dict[str, Any]]]):
     """
     Simplifies a compression argument to a compression method string and
     a dict containing additional arguments.
@@ -253,7 +253,6 @@ def _get_compression_method(compression: Union[str, Dict, None]):
     ------
     ValueError on dict missing 'method' key
     """
-    compression_args = {}  # type: Dict[str, Any]
     # Handle dict
     if isinstance(compression, dict):
         compression_args = compression.copy()
@@ -263,6 +262,8 @@ def _get_compression_method(compression: Union[str, Dict, None]):
         except KeyError:
             raise ValueError("If dict, compression "
                              "must have key 'method'")
+    else:
+        compression_args = {}
     return compression, compression_args
 
 
@@ -318,7 +319,7 @@ def _infer_compression(filepath_or_buffer, compression):
 
 
 def _get_handle(path_or_buf, mode, encoding=None,
-                compression: Union[str, Dict, None] = None,
+                compression: Optional[Union[str, Dict[str, Any]]] = None,
                 memory_map=False, is_text=True):
     """
     Get file handle for given path/buffer and mode.
@@ -464,7 +465,7 @@ class BytesZipFile(zipfile.ZipFile, BytesIO):  # type: ignore
     """
     # GH 17778
     def __init__(self, file, mode, compression=zipfile.ZIP_DEFLATED,
-                 archive_name: Union[str, zipfile.ZipInfo, None] = None,
+                 archive_name: Optional[str] = None,
                  **kwargs):
         if mode in ['wb', 'rb']:
             mode = mode.replace('b', '')

pandas/io/formats/csvs.py

@@ -6,7 +6,7 @@
 import csv as csvlib
 from io import StringIO
 import os
-from typing import Dict, Union
+from typing import Any, Dict, Optional, Union
 import warnings
 from zipfile import ZipFile
 
@@ -28,7 +28,7 @@ class CSVFormatter:
     def __init__(self, obj, path_or_buf=None, sep=",", na_rep='',
                  float_format=None, cols=None, header=True, index=True,
                  index_label=None, mode='w', nanRep=None, encoding=None,
-                 compression: Union[str, Dict, None] = 'infer',
+                 compression: Optional[Union[str, Dict[str, Any]]] = 'infer',
                  quoting=None, line_terminator='\n', chunksize=None,
                  tupleize_cols=False, quotechar='"', date_format=None,
                  doublequote=True, escapechar=None, decimal='.'):

pandas/tests/io/formats/test_to_csv.py

@@ -548,6 +548,13 @@ def test_to_csv_compression_dict(self, compression_only):
             read_df = pd.read_csv(path, index_col=0)
             tm.assert_frame_equal(read_df, df)
 
+    def test_to_csv_compression_dict_no_method(self):
+        # GH 26023
+        df = DataFrame({"ABC": [1]})
+        compression = {"some_option": True}
+        with tm.ensure_clean("out.zip") as path, pytest.raises(ValueError):
+            df.to_csv(path, compression=compression)
+
     @pytest.mark.parametrize("compression", ["zip", "infer"])
     @pytest.mark.parametrize("archive_name", [None, "test_to_csv.csv",
                                               "test_to_csv.zip"])