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BUG: Patch handling no NA values in TextFileReader #15881

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BUG: Patch handling no NA values in TextFileReader #15881

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.20.0.txt
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Expand Up @@ -995,6 +995,7 @@ I/O
- Bug in ``pd.read_csv()`` for the C engine where ``usecols`` were being indexed incorrectly with ``parse_dates`` (:issue:`14792`)
- Bug in ``pd.read_csv()`` with ``parse_dates`` when multiline headers are specified (:issue:`15376`)
- Bug in ``pd.read_csv()`` with ``float_precision='round_trip'`` which caused a segfault when a text entry is parsed (:issue:`15140`)
- Bug in ``pd.read_csv()`` when an index was specified and no values were specified as null values (:issue:`15835`)
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thxs

- Added checks in ``pd.read_csv()`` ensuring that values for ``nrows`` and ``chunksize`` are valid (:issue:`15767`)
- Bug in ``pd.tools.hashing.hash_pandas_object()`` in which hashing of categoricals depended on the ordering of categories, instead of just their values. (:issue:`15143`)
- Bug in ``.to_json()`` where ``lines=True`` and contents (keys or values) contain escaped characters (:issue:`15096`)
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2 changes: 1 addition & 1 deletion pandas/io/parsers.py
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Expand Up @@ -2890,7 +2890,7 @@ def _clean_na_values(na_values, keep_default_na=True):
if keep_default_na:
na_values = _NA_VALUES
else:
na_values = []
na_values = set()
na_fvalues = set()
elif isinstance(na_values, dict):
na_values = na_values.copy() # Prevent aliasing.
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11 changes: 10 additions & 1 deletion pandas/tests/io/parser/na_values.py
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Expand Up @@ -11,7 +11,7 @@
import pandas.io.parsers as parsers
import pandas.util.testing as tm

from pandas import DataFrame, MultiIndex
from pandas import DataFrame, Index, MultiIndex
from pandas.compat import StringIO, range


Expand Down Expand Up @@ -303,3 +303,12 @@ def test_na_values_uint64(self):
expected = DataFrame([[str(2**63), 1], ['', 2]])
out = self.read_csv(StringIO(data), header=None)
tm.assert_frame_equal(out, expected)

def test_empty_na_values_no_default_with_index(self):
# see gh-15835
data = "a,1\nb,2"

expected = DataFrame({'1': [2]}, index=Index(["b"], name="a"))
out = self.read_csv(StringIO(data), keep_default_na=False, index_col=0)

tm.assert_frame_equal(out, expected)