CLN: change to_csv 'legacy' keyword to engine=='python', consistent with c_parser

Author: y-p

pandas/core/format.py

@@ -769,8 +769,9 @@ class CSVFormatter(object):
     def __init__(self, obj, path_or_buf, sep=",", na_rep='', float_format=None,
                cols=None, header=True, index=True, index_label=None,
                mode='w', nanRep=None, encoding=None, quoting=None,
-               line_terminator='\n', chunksize=None,legacy=False):
-        self.legacy=legacy # remove for 0.12
+               line_terminator='\n', chunksize=None, engine=None):
+
+        self.engine = engine  # remove for 0.12
         self.obj = obj
         self.path_or_buf = path_or_buf
         self.sep = sep
@@ -927,7 +928,7 @@ def save(self):
                 self.writer = csv.writer(f, lineterminator=self.line_terminator,
                                          delimiter=self.sep, quoting=self.quoting)
 
-            if self.legacy:
+            if self.engine == 'python':
             # to be removed in 0.12
                 self._helper_csv(self.writer, na_rep=self.na_rep,
                                  float_format=self.float_format, cols=self.cols,

pandas/core/frame.py

@@ -1347,7 +1347,7 @@ def to_csv(self, path_or_buf, sep=",", na_rep='', float_format=None,
                                          float_format=float_format, cols=cols,
                                          header=header, index=index,
                                          index_label=index_label,
-                                         chunksize=chunksize,legacy=kwds.get("legacy",False) )
+                                         chunksize=chunksize,engine=kwds.get("engine") )
             formatter.save()
 
     def to_excel(self, excel_writer, sheet_name='sheet1', na_rep='',