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to_csv writes wrong with NaN value

See original GitHub issue

to_csv with Nan value at top row, unexpected “” in the csv file

import pandas as pd
df = pd.DataFrame([None,1,2])
df.to_csv("df.csv",header=None,index=None,encoding ='utf-8')

# df.csv
#""
#1.0
#2.0

# I want to make df.csv
#
#1.0
#2.0

Versions:

pandas.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 61 Stepping 4, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.20.3
pytest: None
pip: 9.0.1
setuptools: 36.4.0
Cython: None
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: None
patsy: None
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.0.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: 0.9999999
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

Issue Analytics

State:
Created 6 years ago
Comments:23 (21 by maintainers)

Top GitHub Comments

1reaction

Licht-Tcommented, Dec 12, 2017

@jackasser @jreback @gfyoung Actually, the double quoted blank field is the default spec. when writing single column CSV. IOW, this issue is the correct behavior, but the “Case 1” in https://github.com/pandas-dev/pandas/issues/18676#issuecomment-350205767 was wrong behavior. This is now fixed in CPython and the patch is backported to CPython 3.6. https://github.com/python/cpython/pull/4769

Please note that this bug does not exist in CPython 2.7.

0reactions

Licht-Tcommented, Dec 14, 2017

@jreback Okay! (That fix is not released yet, will be included in the next release of CPython 3.6.)

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