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Showing content from https://github.com/pandas-dev/pandas/issues/52266 below:

read_csv with engine='pyarrow' ignores quotechar option · Issue #52266 · pandas-dev/pandas · GitHub

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

import pandas as pd
from io import StringIO

csv = '''example,header
'comma , here',foobar'''

pd.read_csv(StringIO(csv), sep=',', quotechar="'")
'''
Correct output

        example  header
0  comma , here  foobar
'''

pd.read_csv(StringIO(csv), sep=',', quotechar="'", engine='pyarrow')

'''
Error output:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/util/_decorators.py", line 211, in wrapper
    return func(*args, **kwargs)
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/util/_decorators.py", line 331, in wrapper
    return func(*args, **kwargs)
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/io/parsers/readers.py", line 950, in read_csv
    return _read(filepath_or_buffer, kwds)
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/io/parsers/readers.py", line 611, in _read
    return parser.read(nrows)
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/io/parsers/readers.py", line 1766, in read
    df = self._engine.read()  # type: ignore[attr-defined]
  File "/opt/homebrew/lib/python3.10/site-packages/pandas/io/parsers/arrow_parser_wrapper.py", line 147, in read
    table = pyarrow_csv.read_csv(
  File "pyarrow/_csv.pyx", line 1217, in pyarrow._csv.read_csv
  File "pyarrow/_csv.pyx", line 1226, in pyarrow._csv.read_csv
  File "pyarrow/error.pxi", line 144, in pyarrow.lib.pyarrow_internal_check_status
  File "pyarrow/error.pxi", line 100, in pyarrow.lib.check_status
pyarrow.lib.ArrowInvalid: CSV parse error: Expected 2 columns, got 3: 'comma , here',foobar
'''

It appears quotechar is getting ignored. It works if it's double quotes (the default) but no other quote type.

Expected the parse to work (and be the same as non-pyarrow pandas).

I believe the bug is in this bit of code: https://github.com/pandas-dev/pandas/blob/main/pandas/io/parsers/arrow_parser_wrapper.py#L52

Specifically, the pyarrow csv parser seems to want quote_char and pandas is giving quotechar, so this mapping probably needs updated. I have not tested this, though.

commit : 2e218d1
python : 3.10.10.final.0
python-bits : 64
OS : Darwin
OS-release : 21.6.0
Version : Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:35 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T8101
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.5.3
numpy : 1.23.3
pytz : 2022.7.1
dateutil : 2.8.2
setuptools : 67.2.0
pip : 23.0
Cython : 0.29.32
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.9.1
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : 4.11.1
bottleneck : None
brotli : None
fastparquet : None
fsspec : 2022.11.0
gcsfs : None
matplotlib : 3.6.2
numba : 0.56.4
numexpr : None
odfpy : None
openpyxl : 3.0.10
pandas_gbq : None
pyarrow : 11.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : 1.9.3
snappy : None
sqlalchemy : 1.4.45
tables : None
tabulate : 0.9.0
xarray : None
xlrd : None
xlwt : None
zstandard : 0.20.0
tzdata : 2022.5

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