Exploratory commit of what CSVFormatter.save should look like

pandas/io/formats/csvs.py

@@ -30,7 +30,7 @@ class CSVFormatter(object):
     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=None, quoting=None, line_terminator='\n',
+                 compression='infer', quoting=None, line_terminator='\n',
                  chunksize=None, tupleize_cols=False, quotechar='"',
                  date_format=None, doublequote=True, escapechar=None,
                  decimal='.'):
@@ -129,32 +129,12 @@ def save(self):
         if encoding is None:
             encoding = 'ascii' if compat.compat.PY2 else 'utf-8'
 
-        # GH 21227 internal compression is not used when file-like passed.
-        if self.compression and hasattr(self.path_or_buf, 'write'):
-            msg = ("compression has no effect when passing file-like "
-                   "object as input.")
-            warnings.warn(msg, RuntimeWarning, stacklevel=2)
-
-        # when zip compression is called.
-        is_zip = isinstance(self.path_or_buf, ZipFile) or (
-            not hasattr(self.path_or_buf, 'write')
-            and self.compression == 'zip')
-
-        if is_zip:
-            # zipfile doesn't support writing string to archive. uses string
-            # buffer to receive csv writing and dump into zip compression
-            # file handle. GH 21241, 21118
-            f = StringIO()
-            close = False
-        elif hasattr(self.path_or_buf, 'write'):
-            f = self.path_or_buf
-            close = False
-        else:
-            f, handles = _get_handle(self.path_or_buf, self.mode,
-                                     encoding=encoding,
-                                     compression=self.compression)
-            close = True
-
+        f, handles = _get_handle(
+            path_or_buf=self.path_or_buf,
+            mode=self.mode,
+            encoding=encoding,
+            compression=self.compression,
+        )
         try:
             writer_kwargs = dict(lineterminator=self.line_terminator,
                                  delimiter=self.sep, quoting=self.quoting,
@@ -170,21 +150,8 @@ def save(self):
             self._save()
 
         finally:
-            if is_zip:
-                # GH 17778 handles zip compression separately.
-                buf = f.getvalue()
-                if hasattr(self.path_or_buf, 'write'):
-                    self.path_or_buf.write(buf)
-                else:
-                    f, handles = _get_handle(self.path_or_buf, self.mode,
-                                             encoding=encoding,
-                                             compression=self.compression)
-                    f.write(buf)
-                    close = True
-            if close:
-                f.close()
-                for _fh in handles:
-                    _fh.close()
+            for handle in handles:
+                handle.close()
 
     def _save_header(self):