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BUG: fixed chunksize guessed to 0 (py3 only). #8621 #8927

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Merged
merged 1 commit into from
Dec 3, 2014
Merged

BUG: fixed chunksize guessed to 0 (py3 only). #8621 #8927

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.15.2.txt
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Expand Up @@ -99,6 +99,7 @@ Bug Fixes
- 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`)
- Fix negative step support for label-based slices (:issue:`8753`)
- Fixed division by 0 when reading big csv files in python 3 (:issue:`8621`)

Old behavior:

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2 changes: 1 addition & 1 deletion pandas/core/format.py
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Expand Up @@ -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
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8 changes: 8 additions & 0 deletions pandas/tests/test_frame.py
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Expand Up @@ -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)
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