Merge branch 'fix_to_csv_issue_chunksize_8621' of https://github.com/papaloizouc/pandas into papaloizouc-fix_to_csv_issue_chunksize_8621

Conflicts:
	doc/source/whatsnew/v0.15.2.txt

Author: jreback

doc/source/whatsnew/v0.15.2.txt

@@ -90,22 +90,7 @@ Experimental
 
 Bug Fixes
 ~~~~~~~~~
-- Report a ``TypeError`` when invalid/no paramaters are passed in a groupby (:issue:`8015`)
-- Bug in packaging pandas with ``py2app/cx_Freeze`` (:issue:`8602`, :issue:`8831`)
-- Bug in ``groupby`` signatures that didn't include \*args or \*\*kwargs (:issue:`8733`).
-- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo and when it receives no data from Yahoo (:issue:`8761`), (:issue:`8783`).
-- Unclear error message in csv parsing when passing dtype and names and the parsed data is a different data type (:issue:`8833`)
-- Bug in slicing a multi-index with an empty list and at least one boolean indexer (:issue:`8781`)
-- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo (:issue:`8761`).
-- ``Timedelta`` kwargs may now be numpy ints and floats (:issue:`8757`).
-- Fixed several outstanding bugs for ``Timedelta`` arithmetic and comparisons (:issue:`8813`, :issue:`5963`, :issue:`5436`).
-- ``sql_schema`` now generates dialect appropriate ``CREATE TABLE`` statements (:issue:`8697`)
-- ``slice`` string method now takes step into account (:issue:`8754`)
-- Bug in ``BlockManager`` where setting values with different type would break block integrity (:issue:`8850`)
-- Bug in ``DatetimeIndex`` when using ``time`` object as key (:issue:`8667`)
-- Bug in ``merge`` where ``how='left'`` and ``sort=False`` would not preserve left frame order (:issue:`7331`)
 - Fix negative step support for label-based slices (:issue:`8753`)
-- Fix: The font size was only set on x axis if vertical or the y axis if horizontal. (:issue:`8765`)
 
   Old behavior:
 
@@ -130,6 +115,28 @@ Bug Fixes
      s = pd.Series(np.arange(3), ['a', 'b', 'c'])
      s.loc['c':'a':-1]
 
+- Report a ``TypeError`` when invalid/no paramaters are passed in a groupby (:issue:`8015`)
+- Bug in packaging pandas with ``py2app/cx_Freeze`` (:issue:`8602`, :issue:`8831`)
+- Bug in ``groupby`` signatures that didn't include \*args or \*\*kwargs (:issue:`8733`).
+- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo and when it receives no data from Yahoo (:issue:`8761`), (:issue:`8783`).
+- Unclear error message in csv parsing when passing dtype and names and the parsed data is a different data type (:issue:`8833`)
+- Bug in slicing a multi-index with an empty list and at least one boolean indexer (:issue:`8781`)
+- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo (:issue:`8761`).
+- ``Timedelta`` kwargs may now be numpy ints and floats (:issue:`8757`).
+- Fixed several outstanding bugs for ``Timedelta`` arithmetic and comparisons (:issue:`8813`, :issue:`5963`, :issue:`5436`).
+- ``sql_schema`` now generates dialect appropriate ``CREATE TABLE`` statements (:issue:`8697`)
+- ``slice`` string method now takes step into account (:issue:`8754`)
+- Bug in ``BlockManager`` where setting values with different type would break block integrity (:issue:`8850`)
+- Bug in ``DatetimeIndex`` when using ``time`` object as key (:issue:`8667`)
+- Bug in ``merge`` where ``how='left'`` and ``sort=False`` would not preserve left frame order (:issue:`7331`)
+- Fix: The font size was only set on x axis if vertical or the y axis if horizontal. (:issue:`8765`)
+- Fixed division by 0 when reading big csv files in python 3 (:issue:`8621`)
+
+
+
+
+
+
 
 - Imported categorical variables from Stata files retain the ordinal information in the underlying data (:issue:`8836`).
 

pandas/core/format.py

@@ -1247,7 +1247,7 @@ def __init__(self, obj, path_or_buf=None, sep=",", na_rep='', float_format=None,
         self.data = [None] * ncols
 
         if chunksize is None:
-            chunksize = (100000 / (len(self.cols) or 1)) or 1
+            chunksize = (100000 // (len(self.cols) or 1)) or 1
         self.chunksize = int(chunksize)
 
         self.data_index = obj.index

pandas/tests/test_frame.py

@@ -6462,6 +6462,14 @@ def test_to_csv_chunking(self):
                 rs = read_csv(filename,index_col=0)
                 assert_frame_equal(rs, aa)
 
+    def test_to_csv_wide_frame_formatting(self):
+        # Issue #8621
+        df = DataFrame(np.random.randn(1, 100010), columns=None, index=None)
+        with ensure_clean() as filename:
+            df.to_csv(filename, header=False, index=False)
+            rs = read_csv(filename, header=None)
+            assert_frame_equal(rs, df)
+
     def test_to_csv_bug(self):
         f1 = StringIO('a,1.0\nb,2.0')
         df = DataFrame.from_csv(f1, header=None)